Cambridge IGCSE · thinka 原创模拟试题

2024 Cambridge IGCSE Mathematics (0580) 模拟试题及答案详解

Thinka Nov 2024 (V3) Cambridge IGCSE-Style Mock — Mathematics (0580)

200 240 分钟2024
An original Thinka practice paper modelled on the structure and difficulty of the Nov 2024 (V3) Cambridge IGCSE Mathematics (0580) paper. Not affiliated with or reproduced from Cambridge.

卷二 (Extended)

Answer all questions. Electronic calculators should be used where appropriate.
26 题目 · 70.03999999999998
题目 1 · Short Answer
3
Simplify.
$$\frac{4x^2 - 9}{2x^2 + 5x - 12}$$
查看答案详解

解题

Factorise the numerator:
$$4x^2 - 9 = (2x - 3)(2x + 3)$$

Factorise the denominator:
$$2x^2 + 5x - 12 = 2x^2 + 8x - 3x - 12 = 2x(x + 4) - 3(x + 4) = (2x - 3)(x + 4)$$

Simplify by cancelling the common factor $2x - 3$:
$$\frac{(2x - 3)(2x + 3)}{(2x - 3)(x + 4)} = \frac{2x + 3}{x + 4}$$

评分标准

M1 for $(2x - 3)(2x + 3)$
M1 for $(2x - 3)(x + 4)$
A1 for final answer \(\frac{2x + 3}{x + 4}\)
题目 2 · Short Answer
2
In a sale, the price of a bicycle is reduced by 15% to $323.

Calculate the original price of the bicycle.
查看答案详解

解题

Let $P$ be the original price.
Since the price is reduced by 15%, the sale price is 85% of the original price.
$$0.85 \times P = 323$$
$$P = \frac{323}{0.85} = 380$$

评分标准

M1 for $323 \div 0.85$ or $323 \div (1 - 0.15)$
A1 for 380
题目 3 · Short Answer
3
Two mathematically similar vases have heights of 12 cm and 15 cm.
The volume of the smaller vase is $640\text{ cm}^3$.

Calculate the volume of the larger vase.
查看答案详解

解题

Find the linear scale factor:
$$\text{scale factor} = \frac{15}{12} = 1.25$$

Calculate the volume of the larger vase using the cube of the scale factor:
$$\text{Volume} = 640 \times 1.25^3 = 640 \times 1.953125 = 1250\text{ cm}^3$$

评分标准

M1 for linear scale factor $\frac{15}{12}$ oe
M1 for $640 \times (\text{their scale factor})^3$
A1 for 1250
题目 4 · Short Answer
3
In triangle $ABC$, $AB = 7\text{ cm}$, $BC = 8\text{ cm}$ and $AC = 10\text{ cm}$.

Calculate angle $BAC$.
查看答案详解

解题

Using the cosine rule:
$$BC^2 = AB^2 + AC^2 - 2 \cdot AB \cdot AC \cdot \cos(BAC)$$
$$8^2 = 7^2 + 10^2 - 2(7)(10) \cdot \cos(BAC)$$
$$64 = 49 + 100 - 140 \cdot \cos(BAC)$$
$$64 = 149 - 140 \cdot \cos(BAC)$$
$$140 \cdot \cos(BAC) = 85$$
$$\cos(BAC) = \frac{85}{140} = \frac{17}{28}$$
$$\text{angle } BAC = \cos^{-1}\left(\frac{17}{28}\right) \approx 52.624^\circ$$

Rounding to 1 decimal place gives $52.6^\circ$.

评分标准

M1 for $8^2 = 7^2 + 10^2 - 2 \cdot 7 \cdot 10 \cos(BAC)$ or better
M1 for $\cos(BAC) = \frac{85}{140}$ oe
A1 for 52.6 or 52.62...
题目 5 · Short Answer
3
Solve the simultaneous equations.
$$3x - 4y = 17$$
$$x + 3y = -3$$
查看答案详解

解题

Rearrange the second equation to express $x$ in terms of $y$:
$$x = -3 - 3y$$

Substitute into the first equation:
$$3(-3 - 3y) - 4y = 17$$
$$-9 - 9y - 4y = 17$$
$$-13y = 26$$
$$y = -2$$

Substitute $y = -2$ back into the expression for $x$:
$$x = -3 - 3(-2) = -3 + 6 = 3$$

So the solution is $x = 3, y = -2$.

评分标准

M1 for a correct method to eliminate one variable
A1 for $x = 3$ or $y = -2$
A1 for both $x = 3, y = -2$
题目 6 · Short Answer
2
Simplify completely.
$$(64x^9)^{\frac{2}{3}}$$
查看答案详解

解题

Apply the fractional index to each part of the term:
$$(64x^9)^{\frac{2}{3}} = (64)^{\frac{2}{3}} \cdot (x^9)^{\frac{2}{3}}$$

Simplify the constant factor:
$$(64)^{\frac{2}{3}} = (\sqrt[3]{64})^2 = 4^2 = 16$$

Simplify the variable factor:
$$(x^9)^{\frac{2}{3}} = x^{9 \times \frac{2}{3}} = x^6$$

Combining the parts gives:
$$16x^6$$

评分标准

B1 for $16$ or $x^6$ in final answer
B1 for $16x^6$ as final answer
题目 7 · Short Answer
3
Nisha invests $1500 in a savings account.
The account pays compound interest at a rate of 2.4% per year.

Calculate the total interest Nisha has earned at the end of 5 years.
Give your answer correct to the nearest cent.
查看答案详解

解题

Calculate the total amount after 5 years:
$$\text{Amount} = 1500 \times (1 + 0.024)^5 = 1500 \times 1.024^5 \approx 1688.8475...$$

Calculate the interest earned by subtracting the initial principal:
$$\text{Interest} = 1688.8475... - 1500 \approx 188.85$$

评分标准

M1 for $1500 \times 1.024^5$
A1 for 1688.85
A1 for 188.85
题目 8 · Short Answer
2
Find the $n$th term of this sequence:
$$3, \quad 8, \quad 15, \quad 24, \quad \dots$$
查看答案详解

解题

Analyze the differences between the terms:
Terms: 3, 8, 15, 24
First differences: 5, 7, 9
Second differences: 2, 2

Since the second difference is constant at 2, the sequence contains an $n^2$ term with coefficient $\frac{2}{2} = 1$.

Subtract $n^2$ from each term of the sequence:
$$3 - 1^2 = 2$$
$$8 - 2^2 = 4$$
$$15 - 3^2 = 6$$
$$24 - 4^2 = 8$$

The remaining sequence 2, 4, 6, 8, ... corresponds to the linear term $2n$.

Thus, the $n$th term is:
$$n^2 + 2n$$

评分标准

M1 for finding second differences of 2
A1 for $n^2 + 2n$ oe
题目 9 · short_answer
2.69
Simplify completely.

\(\frac{2x^2 - 5x - 3}{4x^2 - 1}\)
查看答案详解

解题

First, factorise the numerator and the denominator.

Numerator:
\(2x^2 - 5x - 3 = (2x + 1)(x - 3)\)

Denominator:
\(4x^2 - 1 = (2x - 1)(2x + 1)\)

Now, rewrite the fraction with these factors:
\(\frac{(2x + 1)(x - 3)}{(2x - 1)(2x + 1)}\)

Cancel the common factor \((2x + 1)\) from the numerator and denominator:
\(\frac{x - 3}{2x - 1}\)

评分标准

M1 for factorising the numerator: \((2x + 1)(x - 3)\) or denominator: \((2x - 1)(2x + 1)\)
M1 for cancelling the common factor \((2x + 1)\)
A1 for correct final answer: \(\frac{x - 3}{2x - 1}\)
题目 10 · short_answer
2.69
The price of a laptop is reduced by 15% in a sale. The sale price is $646. Calculate the original price of the laptop.
查看答案详解

解题

Let the original price be \(P\).
Since the price is reduced by 15%, the sale price is 85% of the original price.
\(0.85P = 646\)
\(P = \frac{646}{0.85} = 760\)

评分标准

M1 for \(646 \div 0.85\) or \(0.85x = 646\)
A1 for 760
题目 11 · short_answer
2.69
A solid metal sphere of radius 4.5 cm is melted down and recast into a solid cone of radius 3 cm.

Calculate the height of the cone.

[The volume, \(V\), of a sphere with radius \(r\) is \(V = \frac{4}{3}\pi r^3\).]
[The volume, \(V\), of a cone with radius \(r\) and height \(h\) is \(V = \frac{1}{3}\pi r^2 h\).]
查看答案详解

解题

Find the volume of the sphere:
\(V_{\text{sphere}} = \frac{4}{3} \pi (4.5)^3 = \frac{4}{3} \pi (91.125) = 121.5 \pi\)

Since the sphere is recast into a cone, the volume of the cone is equal to the volume of the sphere:
\(V_{\text{cone}} = \frac{1}{3} \pi (3)^2 h = 3 \pi h\)

Equating the volumes:
\(3 \pi h = 121.5 \pi\)
\(3h = 121.5\)
\(h = 40.5\)

评分标准

M1 for setting up the volume of sphere: \(\frac{4}{3} \pi (4.5)^3\) (or \(121.5\pi\))
M1 for equating their sphere volume to the cone volume formula: \(3\pi h = \text{their } V_{\text{sphere}}\)
A1 for 40.5
题目 12 · short_answer
2.69
In triangle \(ABC\), \(AB = 7\) cm, \(BC = 9\) cm and angle \(ABC = 64^\circ\).

Calculate the length of \(AC\), giving your answer correct to 3 significant figures.
查看答案详解

解题

Use the Cosine Rule to find the length of \(AC\):
\(AC^2 = AB^2 + BC^2 - 2(AB)(BC)\cos(ABC)\)
\(AC^2 = 7^2 + 9^2 - 2(7)(9)\cos(64^\circ)\)
\(AC^2 = 49 + 81 - 126\cos(64^\circ)\)
\(AC^2 = 130 - 55.235\)
\(AC^2 = 74.765\)
\(AC = \sqrt{74.765} \approx 8.6467\)

To 3 significant figures, \(AC = 8.65\) cm.

评分标准

M1 for substituting correctly into the cosine rule: \(7^2 + 9^2 - 2(7)(9)\cos(64^\circ)\)
A1 for \(AC^2 = 74.76\dots\) or better
A1 for 8.65
题目 13 · short_answer
2.69
Rearrange the formula to make \(x\) the subject.

\(y = \frac{3x + 2}{5 - x}\)
查看答案详解

解题

Multiply both sides by \((5 - x)\):
\(y(5 - x) = 3x + 2\)
\(5y - xy = 3x + 2\)

Group terms with \(x\) on one side and other terms on the other side:
\(5y - 2 = 3x + xy\)

Factor out \(x\) on the right side:
\(5y - 2 = x(3 + y)\)

Divide by \((3 + y)\):
\(x = \frac{5y - 2}{y + 3}\)

评分标准

M1 for clearing the fraction: \(y(5 - x) = 3x + 2\)
M1 for isolating terms with \(x\): \(5y - 2 = 3x + xy\)
A1 for correct final formula: \(x = \frac{5y - 2}{y + 3}\) (or equivalent)
题目 14 · short_answer
2.69
Solve the simultaneous equations.

\(5x + 2y = 16\)
\(3x - 4y = 7\)
查看答案详解

解题

Multiply the first equation by 2 to make the coefficients of \(y\) equal in magnitude:
\(10x + 4y = 32\)

Now add this equation to the second equation:
\((10x + 4y) + (3x - 4y) = 32 + 7\)
\(13x = 39\)
\(x = 3\)

Substitute \(x = 3\) back into the first equation:
\(5(3) + 2y = 16\)
\(15 + 2y = 16\)
\(2y = 1\)
\(y = 0.5\)

So, the solution is \(x = 3\) and \(y = 0.5\).

评分标准

M1 for a correct method to eliminate one variable (e.g. multiplying the first equation by 2)
A1 for \(x = 3\)
A1 for \(y = 0.5\)
题目 15 · short_answer
2.69
Simplify completely.

\((64x^6 y^{-12})^{\frac{2}{3}}\)
查看答案详解

解题

Apply the power of \(\frac{2}{3}\) to each term inside the bracket:
\((64)^{\frac{2}{3}} \cdot (x^6)^{\frac{2}{3}} \cdot (y^{-12})^{\frac{2}{3}}\)

Simplify each term:
\((64)^{\frac{2}{3}} = (\sqrt[3]{64})^2 = 4^2 = 16\)
\((x^6)^{\frac{2}{3}} = x^{6 \times \frac{2}{3}} = x^4\)
\((y^{-12})^{\frac{2}{3}} = y^{-12 \times \frac{2}{3}} = y^{-8}\)

Combine the terms:
\(16x^4 y^{-8} = \frac{16x^4}{y^8}\)

评分标准

B1 for \((64)^{\frac{2}{3}} = 16\)
B1 for \((x^6)^{\frac{2}{3}} = x^4\) or \((y^{-12})^{\frac{2}{3}} = y^{-8}\)
B1 for fully simplified expression: \(16x^4 y^{-8}\) or \(\frac{16x^4}{y^8}\)
题目 16 · short_answer
2.69
Solve the quadratic equation \(3x^2 - 7x - 5 = 0\).

Show all your working and give your answers correct to 2 decimal places.
查看答案详解

解题

Use the quadratic formula:
\(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\)

Here, \(a = 3\), \(b = -7\), and \(c = -5\):
\(x = \frac{-(-7) \pm \sqrt{(-7)^2 - 4(3)(-5)}}{2(3)}\)
\(x = \frac{7 \pm \sqrt{49 + 60}}{6}\)
\(x = \frac{7 \pm \sqrt{109}}{6}\)

Calculate the two roots:
\(x = \frac{7 + 10.4403}{6} \approx 2.91\)
\(x = \frac{7 - 10.4403}{6} \approx -0.57\)

评分标准

M1 for substituting correctly into the formula: \(\frac{-(-7) \pm \sqrt{(-7)^2 - 4(3)(-5)}}{2(3)}\)
A1 for \(\sqrt{109}\) seen or implied
A1 for 2.91 and -0.57
题目 17 · Short Answer
2.69
Simplify. \[\frac{2a - 3ab + 2c - 3bc}{4 - 9b^2}\]
查看答案详解

解题

First, factorise the numerator by grouping:
\(2a - 3ab + 2c - 3bc = a(2 - 3b) + c(2 - 3b) = (2 - 3b)(a + c)\).

Next, factorise the denominator as a difference of two squares:
\(4 - 9b^2 = (2 - 3b)(2 + 3b)\).

Now divide the numerator by the denominator:
\(\frac{(2 - 3b)(a + c)}{(2 - 3b)(2 + 3b)} = \frac{a + c}{2 + 3b}\).

评分标准

M1 for factorising the numerator to \((2-3b)(a+c)\) oe
M1 for factorising the denominator to \((2-3b)(2+3b)\) oe
A1 for the correct simplified fraction
题目 18 · Short Answer
2.69
Solve the simultaneous equations.
\[4x - 3y = 18\]
\[3x + 2y = 22\]
查看答案详解

解题

Multiply the first equation by 2:
\(8x - 6y = 36\)

Multiply the second equation by 3:
\(9x + 6y = 66\)

Add the two equations to eliminate \(y\):
\(17x = 102\)
\(x = 6\)

Substitute \(x = 6\) into the second equation:
\(3(6) + 2y = 22\)
\(18 + 2y = 22\)
\(2y = 4\)
\(y = 2\)

评分标准

M1 for a correct method to eliminate one variable (e.g. equating coefficients)
A1 for finding one variable correctly (e.g., \(x=6\) or \(y=2\))
A1 for finding both variables correctly
题目 19 · Short Answer
2.69
Two mathematically similar cylinders have total surface areas \(180\text{ cm}^2\) and \(80\text{ cm}^2\).
The volume of the larger cylinder is \(243\text{ cm}^3\).
Calculate the volume of the smaller cylinder.
查看答案详解

解题

The ratio of the total surface areas of the similar cylinders is:
\(\frac{A_{\text{large}}}{A_{\text{small}}} = \frac{180}{80} = \frac{9}{4}\).

Since the cylinders are mathematically similar, the linear scale factor \(k\) is:
\(k = \sqrt{\frac{9}{4}} = \frac{3}{2}\).

The volume scale factor is:
\(k^3 = \left(\frac{3}{2}\right)^3 = \frac{27}{8}\).

Therefore, the volume of the smaller cylinder is:
\(V_{\text{small}} = \frac{V_{\text{large}}}{k^3} = \frac{243}{\frac{27}{8}} = 243 \times \frac{8}{27} = 9 \times 8 = 72\text{ cm}^3\).

评分标准

M1 for finding the linear scale factor \(\sqrt{\frac{180}{80}}\) or \(1.5\) (or reciprocal)
M1 for cubing their linear scale factor to obtain \(3.375\) (or reciprocal)
A1 for 72
题目 20 · Short Answer
2.69
An antique clock is sold at an auction for $1536.
This sale price includes a buyer's premium of 20% that is added to the hammer price.
Calculate the hammer price of the clock.
查看答案详解

解题

Let \(H\) be the hammer price.
The total sale price is the hammer price plus 20% of the hammer price:
\(1.20 \times H = 1536\).

To find the hammer price:
\(H = \frac{1536}{1.20} = 1280\).

评分标准

M2 for \(1536 \div 1.20\) oe
(or M1 for equating \(120\%\) to \(1536\))
A1 for 1280
题目 21 · Short Answer
2.69
In triangle \(ABC\), \(AB = 8.4\text{ cm}\), \(AC = 11.5\text{ cm}\) and angle \(BAC = 52^\circ\).
Calculate the length of \(BC\).
Give your answer correct to 3 significant figures.
查看答案详解

解题

Using the cosine rule:
\[BC^2 = AB^2 + AC^2 - 2(AB)(AC)\cos(BAC)\]
\[BC^2 = 8.4^2 + 11.5^2 - 2(8.4)(11.5)\cos(52^\circ)\]
\[BC^2 = 70.56 + 132.25 - 193.2\cos(52^\circ)\]
\[BC^2 \approx 202.81 - 193.2(0.61566) \approx 202.81 - 118.946 = 83.864\]
\[BC = \sqrt{83.864} \approx 9.1577\text{ cm}\]
Correct to 3 significant figures, the length is \(9.16\text{ cm}\).

评分标准

M1 for correct substitution into the Cosine Rule: \(8.4^2 + 11.5^2 - 2(8.4)(11.5)\cos(52)\)
M1 for \(BC^2 \approx 83.9\) (or better)
A1 for 9.16 (or 9.157 to 9.158)
题目 22 · Short Answer
2.69
Simplify.
\[(64x^{12})^{-\frac{2}{3}}\]
查看答案详解

解题

Apply the exponent to each factor inside the brackets:
\((64)^{-\frac{2}{3}} \times (x^{12})^{-\frac{2}{3}}\)

Simplify the numerical part:
\(64^{-\frac{2}{3}} = \frac{1}{(\sqrt[3]{64})^2} = \frac{1}{4^2} = \frac{1}{16}\)

Simplify the algebraic part:
\((x^{12})^{-\frac{2}{3}} = x^{12 \times \left(-\frac{2}{3}\right)} = x^{-8}\)

Combine the results:
\(\frac{1}{16}x^{-8} = \frac{1}{16x^8}\).

评分标准

M1 for obtaining \(64^{-\frac{2}{3}} = \frac{1}{16}\) or \((x^{12})^{-\frac{2}{3}} = x^{-8}\)
A1 for the correct final answer of \(\frac{1}{16x^8}\) or \(\frac{1}{16}x^{-8}\)
题目 23 · Short Answer
2.69
Two mathematically similar photographs have widths of \(15\text{ cm}\) and \(18\text{ cm}\).
The area of the smaller photograph is \(225\text{ cm}^2\).
Calculate the area of the larger photograph.
查看答案详解

解题

First, find the scale factor of lengths:
\(k = \frac{18}{15} = 1.2\).

Since the photographs are mathematically similar, the scale factor of areas is:
\(k^2 = 1.2^2 = 1.44\).

Multiply the area of the smaller photograph by the area scale factor:
\(\text{Area of larger photograph} = 225 \times 1.44 = 324\text{ cm}^2\).

评分标准

M1 for finding the length scale factor \(\frac{18}{15}\) or \(1.2\)
M1 for squaring their length scale factor to get \(1.44\)
A1 for 324
题目 24 · Short Answer
2.69
A drawer contains 5 blue socks and 4 red socks.
Two socks are taken from the drawer at random, one after the other, without replacement.
Find the probability that the two socks are of different colours.
查看答案详解

解题

The total number of socks is \(5 + 4 = 9\).

The socks are different colours if we choose (Blue then Red) or (Red then Blue):

\(P(\text{Blue then Red}) = \frac{5}{9} \times \frac{4}{8} = \frac{20}{72}\)

\(P(\text{Red then Blue}) = \frac{4}{9} \times \frac{5}{8} = \frac{20}{72}\)

Add these two probabilities together:
\(P(\text{Different Colours}) = \frac{20}{72} + \frac{20}{72} = \frac{40}{72} = \frac{5}{9}\).

评分标准

M1 for \(\frac{5}{9} \times \frac{4}{8}\) or \(\frac{4}{9} \times \frac{5}{8}\) oe
M1 for adding two correct probabilities
A1 for \(\frac{5}{9}\) or equivalent fraction/decimal (0.556 or 0.5555...)
题目 25 · short_answer
3
Rearrange the formula to make \(t\) the subject.

\[w = \frac{4t + 1}{3 - t}\]
查看答案详解

解题

Multiply both sides by \(3 - t\):
\(w(3 - t) = 4t + 1\)

Expand the brackets:
\(3w - wt = 4t + 1\)

Rearrange to gather terms with \(t\) on one side and the other terms on the other side:
\(3w - 1 = 4t + wt\)

Factorise \(t\) on the right-hand side:
\(3w - 1 = t(4 + w)\)

Divide by \(4 + w\):
\(t = \frac{3w - 1}{w + 4}\)

评分标准

M1 for multiplying by \(3 - t\) to get \(w(3 - t) = 4t + 1\) or better
M1 for isolating terms containing \(t\) on one side, e.g. \(3w - 1 = t(4 + w)\) oe
A1 for \(t = \frac{3w - 1}{w + 4}\) or equivalent
题目 26 · short_answer
3
The value of a rare book increases by \(r\%\) each year.
Over a period of 3 years, the value of the book increases from $150 to $199.65.

Calculate the value of \(r\).
查看答案详解

解题

Using the compound growth formula:
\[150 \times \left(1 + \frac{r}{100}\right)^3 = 199.65\]

Divide both sides by 150:
\[\left(1 + \frac{r}{100}\right)^3 = \frac{199.65}{150}\]
\[\left(1 + \frac{r}{100}\right)^3 = 1.331\]

Take the cube root of both sides:
\[1 + \frac{r}{100} = \sqrt[3]{1.331}\]
\[1 + \frac{r}{100} = 1.1\]

Subtract 1 from both sides:
\[\frac{r}{100} = 0.1\]

Multiply by 100:
\[r = 10\]

评分标准

M1 for setting up the equation \(150 \times \left(1 + \frac{r}{100}\right)^3 = 199.65\) or \(150 \times k^3 = 199.65\)
M1 for taking the cube root, e.g., \(\sqrt[3]{\frac{199.65}{150}}\) or \(1.1\) seen
A1 for \(10\)

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Paper 4 (Extended)

Answer all questions. Show all necessary working clearly. Non-exact numerical answers should be rounded to 3 significant figures unless specified.
12 题目 · 132
题目 1 · Structured Long Answer
11
Alistair invests some money in different schemes.

(a) Alistair invests \(\$6500\) at a rate of \(3.2\%\) per year simple interest. Calculate the total interest earned at the end of 8 years. [3]

(b) Bianca invests \(\$6500\) at a rate of \(2.9\%\) per year compound interest. Calculate the total value of her investment at the end of 8 years. Give your answer correct to the nearest dollar. [3]

(c) Charles invests \(\$5000\) in a savings account where interest is compounded annually. At the end of 12 years, the investment is worth \(\$7340\). Calculate the annual percentage rate of compound interest, correct to 2 decimal places. [5]
查看答案详解

解题

(a) Simple interest formula: \(I = \frac{P \times R \times T}{100}\)
\(I = \frac{6500 \times 3.2 \times 8}{100} = 1664\)

(b) Compound interest formula: \(A = P \left(1 + \frac{R}{100}\right)^t\)
\(A = 6500 \times (1.029)^8 \approx 8168.37\)
To the nearest dollar, the value is \(\$8168\).

(c) \(5000 \times \left(1 + \frac{r}{100}\right)^{12} = 7340\)
\(\left(1 + \frac{r}{100}\right)^{12} = 1.468\)
\(1 + \frac{r}{100} = (1.468)^{\frac{1}{12}} \approx 1.03239\)
\(\frac{r}{100} = 0.03239 \implies r = 3.24\%\)

评分标准

(a)
M1 for \(6500 \times 0.032 \times 8\) oe
A1 for 1664

(b)
M1 for \(6500 \times (1.029)^8\) oe
A1 for 8168.37 or 8168
A1 for 8168 (nearest dollar)

(c)
M1 for \(5000 \times (1 + r/100)^{12} = 7340\)
M1 for \((1 + r/100)^{12} = 1.468\)
M1 for \(1 + r/100 = 1.468^{1/12}\)
A1 for 1.03239...
A1 for 3.24
题目 2 · Structured Long Answer
11
(a) Simplify completely: \(\frac{2x^2 - 8}{x^2 + 5x + 6}\). [4]

(b) Write as a single fraction in its simplest form: \(\frac{3}{2a-1} - \frac{2}{a+3}\). [4]

(c) Expand and simplify: \((2y - 3)(y^2 - 4y + 5)\). [3]
查看答案详解

解题

(a) Factorise the numerator: \(2x^2 - 8 = 2(x^2 - 4) = 2(x - 2)(x + 2)\)
Factorise the denominator: \(x^2 + 5x + 6 = (x + 2)(x + 3)\)
Cancel out common factor \((x + 2)\):
\(\frac{2(x - 2)(x + 2)}{(x + 2)(x + 3)} = \frac{2(x - 2)}{x + 3} = \frac{2x - 4}{x + 3}\)

(b) Find a common denominator: \((2a - 1)(a + 3)\)
\(\frac{3(a + 3) - 2(2a - 1)}{(2a - 1)(a + 3)} = \frac{3a + 9 - 4a + 2}{(2a - 1)(a + 3)} = \frac{11 - a}{(2a - 1)(a + 3)}\)

(c) Multiply term by term:
\((2y - 3)(y^2 - 4y + 5) = 2y(y^2 - 4y + 5) - 3(y^2 - 4y + 5)\)
\(= 2y^3 - 8y^2 + 10y - 3y^2 + 12y - 15\)
\(= 2y^3 - 11y^2 + 22y - 15\)

评分标准

(a)
M1 for factorising numerator: \(2(x-2)(x+2)\) oe
M1 for factorising denominator: \((x+2)(x+3)\) oe
M1 for canceling \((x+2)\)
A1 for final answer \(\frac{2x-4}{x+3}\)

(b)
M1 for \(3(a+3) - 2(2a-1)\) oe
M1 for expanding numerator to \(3a + 9 - 4a + 2\)
M1 for common denominator \((2a-1)(a+3)\) seen
A1 for final answer \(\frac{11-a}{(2a-1)(a+3)}\)

(c)
M1 for partial expansion with at least 3 correct terms
M1 for fully expanded unsimplified expression: \(2y^3 - 8y^2 + 10y - 3y^2 + 12y - 15\)
A1 for final simplified expression: \(2y^3 - 11y^2 + 22y - 15\)
题目 3 · Structured Long Answer
11
A rectangular garden has length \((2x + 5)\) m and width \((x - 1)\) m.

(a) The area of the garden is \(42 \text{ m}^2\). Show that \(2x^2 + 3x - 47 = 0\). [3]

(b) Solve the equation \(2x^2 + 3x - 47 = 0\). Show all your working and give your answers correct to 2 decimal places. [5]

(c) Find the perimeter of the garden using the valid value of \(x\). [3]
查看答案详解

解题

(a) Area = Length \(\times\) Width
\((2x + 5)(x - 1) = 42\)
\(2x^2 - 2x + 5x - 5 = 42\)
\(2x^2 + 3x - 5 - 42 = 0\)
\(2x^2 + 3x - 47 = 0\) (Shown)

(b) Using the quadratic formula: \(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\)
\(x = \frac{-3 \pm \sqrt{3^2 - 4(2)(-47)}}{2(2)}\)
\(x = \frac{-3 \pm \sqrt{9 + 376}}{4} = \frac{-3 \pm \sqrt{385}}{4}\)
\(x = \frac{-3 \pm 19.6214}{4}\)
\(x = 4.155 \approx 4.16\) or \(x = -5.655 \approx -5.66\)

(c) Since width cannot be negative, we use \(x = 4.155\).
Length = \(2(4.155) + 5 = 13.31\) m
Width = \(4.155 - 1 = 3.155\) m
Perimeter = \(2 \times (13.31 + 3.155) = 2 \times 16.465 = 32.93\) m, which is \(32.9\) m (to 3 sf).

评分标准

(a)
M1 for \((2x + 5)(x - 1) = 42\)
M1 for \(2x^2 - 2x + 5x - 5 = 42\)
A1 for final step showing equation in standard form with no errors

(b)
M1 for substituting correct values into quadratic formula
B1 for \(\sqrt{385}\) or \(3^2 - 4(2)(-47)\)
M1 for splitting into two cases
A1 for \(4.16\) (accept \(4.155\) to \(4.16\))
A1 for \(-5.66\) (accept \(-5.655\) to \(-5.66\))

(c)
M1 for selecting positive root \(x \approx 4.16\)
M1 for substituting into \(2(2x+5 + x-1)\) or equivalent
A1 for \(32.9\) or \(32.93\)
题目 4 · Structured Long Answer
11
A toy is made of a hemisphere of radius \(r\) and a cone of radius \(r\) and height \(h\), joined together at their circular bases.

(a) The radius of the hemisphere is \(6\text{ cm}\) and the height of the cone is \(14\text{ cm}\). Calculate the total volume of the toy. [3]

(b) Show that the slant height of the cone is \(15.23\text{ cm}\), correct to 2 decimal places. [2]

(c) Calculate the total surface area of the toy. [The curved surface area of a cone with radius \(r\) and slant height \(l\) is \(\pi r l\). The curved surface area of a sphere with radius \(r\) is \(4\pi r^2\).] [4]

(d) The toy is made of plastic with a density of \(1.15\text{ g/cm}^3\). Calculate the total mass of the toy. [2]
查看答案详解

解题

(a) Volume of hemisphere = \(\frac{2}{3} \pi r^3 = \frac{2}{3} \pi (6)^3 = 144\pi \approx 452.39\text{ cm}^3\)
Volume of cone = \(\frac{1}{3} \pi r^2 h = \frac{1}{3} \pi (6)^2 (14) = 168\pi \approx 527.79\text{ cm}^3\)
Total volume = \(144\pi + 168\pi = 312\pi \approx 980.18\text{ cm}^3\) (or \(980\text{ cm}^3\))

(b) Slant height \(l = \sqrt{r^2 + h^2} = \sqrt{6^2 + 14^2} = \sqrt{36 + 196} = \sqrt{232} \approx 15.2315\text{ cm}\)
Which rounds to \(15.23\text{ cm}\) (Shown)

(c) Total Surface Area = Curved Surface Area of Cone + Curved Surface Area of Hemisphere
\(\text{Curved surface area of cone} = \pi r l = \pi \times 6 \times 15.2315 \approx 287.10\text{ cm}^2\)
\(\text{Curved surface area of hemisphere} = 2\pi r^2 = 2 \pi (6)^2 = 72\pi \approx 226.19\text{ cm}^2\)
Total Surface Area = \(287.10 + 226.19 = 513.29\text{ cm}^2\) (or \(513\text{ cm}^2\))

(d) Mass = \(\text{Density} \times \text{Volume} = 1.15 \times 980.18 = 1127.2\text{ g}\) (or \(1130\text{ g}\) to 3 sf)

评分标准

(a)
M1 for Volume of hemisphere = \(\frac{2}{3} \pi \times 6^3\)
M1 for Volume of cone = \(\frac{1}{3} \pi \times 6^2 \times 14\)
A1 for total volume of \(980\) or \(980.18\)

(b)
M1 for \(\sqrt{6^2 + 14^2}\) oe
A1 for showing \(15.2315...\) and rounding to \(15.23\)

(c)
M1 for curved area of cone = \(\pi \times 6 \times 15.23\)
M1 for curved area of hemisphere = \(2 \times \pi \times 6^2\)
M1 for adding the two areas
A1 for \(513\) or \(513.29\)

(d)
M1 for \(1.15 \times \text{their (a)}\)
A1 for \(1130\) (or \(1127.2\))
题目 5 · Structured Long Answer
11
A triangular field \(PQR\) has sides \(PQ = 75\text{ m}\), \(QR = 110\text{ m}\) and angle \(PQR = 58^\circ\).

(a) Calculate the distance \(PR\). [4]

(b) Calculate the angle \(QPR\). [4]

(c) Calculate the area of the field. [3]
查看答案详解

解题

(a) Using the Cosine Rule:
\(PR^2 = PQ^2 + QR^2 - 2 \times PQ \times QR \times \cos(PQR)\)
\(PR^2 = 75^2 + 110^2 - 2 \times 75 \times 110 \times \cos(58^\circ)\)
\(PR^2 = 5625 + 12100 - 16500 \times 0.52992\)
\(PR^2 = 17725 - 8743.66 = 8981.34\)
\(PR = \sqrt{8981.34} \approx 94.77\text{ m}\)
PR is \(94.8\text{ m}\) (to 3 sf).

(b) Using the Cosine Rule (or Sine Rule):
\(\cos(QPR) = \frac{PQ^2 + PR^2 - QR^2}{2 \times PQ \times PR}\)
\(\cos(QPR) = \frac{75^2 + 94.77^2 - 110^2}{2 \times 75 \times 94.77}\)
\(\cos(QPR) = \frac{5625 + 8981.36 - 12100}{14215.5} = \frac{2506.36}{14215.5} \approx 0.17631\)
\(\text{Angle } QPR = \cos^{-1}(0.17631) \approx 79.84^\circ\)
Angle QPR is \(79.8^\circ\) (to 3 sf).

(c) Area of the triangle = \(\frac{1}{2} \times a \times b \times \sin(C)\)
\(\text{Area} = \frac{1}{2} \times 75 \times 110 \times \sin(58^\circ)\)
\(\text{Area} = 4125 \times 0.84805 \approx 3498.2\text{ m}^2\)
Area of field is \(3500\text{ m}^2\) (to 3 sf).

评分标准

(a)
M1 for Cosine Rule formula correctly identified
M2 for \(75^2 + 110^2 - 2 \times 75 \times 110 \times \cos(58^\circ)\)
A1 for \(94.8\) or \(94.77\)

(b)
M1 for Sine Rule or Cosine Rule setup: \(\frac{\sin(QPR)}{110} = \frac{\sin(58)}{94.77}\) oe
M2 for isolating \(\sin(QPR)\) or \(\cos(QPR)\)
A1 for \(79.8\) or \(79.84\)

(c)
M1 for Area formula: \(\frac{1}{2} a b \sin(C)\)
M1 for \(0.5 \times 75 \times 110 \times \sin(58)\)
A1 for \(3500\) or \(3498\)
题目 6 · Structured Long Answer
11
(a) Make \(t\) the subject of the formula: \(w = \frac{3t + 2}{5 - t}\). [4]

(b) Given functions \(f(x) = 3x - 1\) and \(g(x) = \frac{x+2}{2x-3}\), where \(x \neq 1.5\).

(i) Find \(g^{-1}(x)\). [4]

(ii) Find \(fg(4)\). [3]
查看答案详解

解题

(a) Multiply both sides by \((5 - t)\):
\(w(5 - t) = 3t + 2\)
\(5w - wt = 3t + 2\)
Collect terms with \(t\) on one side:
\(5w - 2 = 3t + wt\)
Factorise \(t\):
\(5w - 2 = t(3 + w)\)
\(t = \frac{5w - 2}{w + 3}\)

(b)(i) Let \(y = \frac{x+2}{2x-3}\)
Swap \(x\) and \(y\):
\(x = \frac{y+2}{2y-3}\)
\(x(2y - 3) = y + 2\)
\(2xy - 3x = y + 2\)
\(2xy - y = 3x + 2\)
\(y(2x - 1) = 3x + 2\)
\(y = \frac{3x+2}{2x-1}\)
Therefore, \(g^{-1}(x) = \frac{3x+2}{2x-1}\).

(b)(ii) First find \(g(4)\):
\(g(4) = \frac{4+2}{2(4)-3} = \frac{6}{5} = 1.2\)
Now find \(f(1.2)\):
\(f(1.2) = 3(1.2) - 1 = 3.6 - 1 = 2.6\)

评分标准

(a)
M1 for \(w(5 - t) = 3t + 2\)
M1 for expanding: \(5w - wt = 3t + 2\)
M1 for isolating terms with \(t\): \(t(3 + w) = 5w - 2\) oe
A1 for \(t = \frac{5w - 2}{w + 3}\)

(b)(i)
M1 for changing the subject of \(y = g(x)\)
M1 for \(2xy - 3x = y + 2\) oe
M1 for factorising \(y\): \(y(2x - 1) = 3x + 2\)
A1 for \(\frac{3x+2}{2x-1}\)

(b)(ii)
M1 for \(g(4) = \frac{6}{5}\) or \(1.2\)
M1 for substituting their \(g(4)\) into \(f(x)\)
A1 for \(2.6\)
题目 7 · Structured Long Answer
11
A shopkeeper buys shirts and jackets in the ratio \(5 : 3\).

(a) The shopkeeper buys a total of 120 items. Calculate the number of jackets purchased. [2]

(b) He pays \(\$15\) for each shirt and \(\$35\) for each jacket. Calculate the total amount he pays for the 120 items. [3]

(c) He sells the shirts at a profit of \(40\%\) and the jackets at \(\$48\) each. Calculate his total percentage profit on the entire transaction. [6]
查看答案详解

解题

(a) Total parts = \(5 + 3 = 8\)
Number of jackets = \(\frac{3}{8} \times 120 = 45\)

(b) Number of shirts = \(120 - 45 = 75\)
Total cost of shirts = \(75 \times 15 = \$1125\)
Total cost of jackets = \(45 \times 35 = \$1575\)
Total cost = \(1125 + 1575 = \$2700\)

(c) Selling price of each shirt = \(15 \times 1.40 = \$21\)
Total revenue from shirts = \(75 \times 21 = \$1575\)
Total revenue from jackets = \(45 \times 48 = \$2160\)
Total revenue = \(1575 + 2160 = \$3735\)
Total profit = \(3735 - 2700 = \$1035\)
Percentage profit = \(\frac{1035}{2700} \times 100 = 38.33\%\)
Total percentage profit is \(38.3\%\) (to 3 sf).

评分标准

(a)
M1 for \(\frac{3}{8} \times 120\)
A1 for 45

(b)
M1 for finding shirts = 75
M1 for \((75 \times 15) + (45 \times 35)\)
A1 for 2700

(c)
M1 for shirt selling price: \(15 \times 1.40 = 21\)
M1 for total shirt sales: \(75 \times 21 = 1575\)
M1 for total jacket sales: \(45 \times 48 = 2160\)
M1 for total revenue: 3735 or total profit: 1035
M1 for \(\frac{\text{their } 1035}{2700} \times 100\)
A1 for 38.3
题目 8 · Structured Long Answer
11
A curve has equation \(y = x^3 - 6x^2 + 9x + 5\).

(a) Find \(\frac{dy}{dx}\). [2]

(b) Find the coordinates of the two turning points on this curve. [5]

(c) Find the equation of the tangent to the curve at the point where \(x = 2\). Give your answer in the form \(y = mx + c\). [4]
查看答案详解

解题

(a) Differentiate term-by-term:
\(\frac{dy}{dx} = 3x^2 - 12x + 9\)

(b) For turning points, set \(\frac{dy}{dx} = 0\):
\(3x^2 - 12x + 9 = 0\)
\(3(x^2 - 4x + 3) = 0\)
\(3(x - 1)(x - 3) = 0\)
So, \(x = 1\) or \(x = 3\)

When \(x = 1\):
\(y = 1^3 - 6(1)^2 + 9(1) + 5 = 1 - 6 + 9 + 5 = 9\)
Turning point: \((1, 9)\)

When \(x = 3\):
\(y = 3^3 - 6(3)^2 + 9(3) + 5 = 27 - 54 + 27 + 5 = 5\)
Turning point: \((3, 5)\)

(c) At \(x = 2\):
Gradient of tangent, \(m = \left. \frac{dy}{dx} \right|_{x=2} = 3(2)^2 - 12(2) + 9 = 12 - 24 + 9 = -3\)
Y-coordinate, \(y = 2^3 - 6(2)^2 + 9(2) + 5 = 8 - 24 + 18 + 5 = 7\)
So point of tangency is \((2, 7)\).

Using \(y = mx + c\):
\(7 = -3(2) + c \implies 7 = -6 + c \implies c = 13\)
Equation is \(y = -3x + 13\).

评分标准

(a)
M1 for 2 correct differentiated terms
A1 for \(3x^2 - 12x + 9\)

(b)
M1 for setting \(\text{their } \frac{dy}{dx} = 0\)
M1 for factorising or solving: \(3(x-1)(x-3) = 0\)
A1 for \(x = 1\) and \(x = 3\)
A1 for \(y = 9\) (when \(x = 1\))
A1 for \(y = 5\) (when \(x = 3\))

(c)
M1 for substituting \(x = 2\) into \(\text{their } \frac{dy}{dx}\) to get \(m = -3\)
M1 for substituting \(x = 2\) into original equation to get \(y = 7\)
M1 for substituting \((2, 7)\) and \(m = -3\) into \(y = mx + c\) oe
A1 for \(y = -3x + 13\)
题目 9 · Structured Long Answer
11
Elena has some money to invest.

(a) She invests $4500 in an account paying 3.2% per year compound interest. Calculate the total value of her investment at the end of 8 years. Give your answer correct to the nearest dollar.

(b) She also invests $3000 in another account paying simple interest. At the end of 6 years, the total amount in this account is $3576. Calculate the rate of simple interest per year.

(c) The value of Elena's house increased by 15% in 2022, and then decreased by 8% in 2023. At the end of 2023, the house was valued at $264,500. Calculate the value of the house at the start of 2022.
查看答案详解

解题

(a)
\(A = P \left(1 + \frac{r}{100}\right)^t\)
\(A = 4500 \left(1 + \frac{3.2}{100}\right)^8 = 4500(1.032)^8 \approx 5790.15\)
Correct to the nearest dollar: $5790

(b)
Total simple interest earned over 6 years = \(3576 - 3000 = 576\)
Simple interest per year = \(\frac{576}{6} = 96\)
Rate of simple interest \(r = \frac{96}{3000} \times 100 = 3.2\%\)

(c)
Let the initial value at the start of 2022 be \(V\).
Value at the end of 2022 = \(1.15V\)
Value at the end of 2023 = \(1.15V \times 0.92 = 1.058V\)
Given: \(1.058V = 264500\)
\(V = \frac{264500}{1.058} = 250000\)

评分标准

(a) [3 marks]
M1 for \(4500 \times (1.032)^8\)
A1 for 5790.15
A1 for 5790 (correct to the nearest dollar)

(b) [3 marks]
M1 for \(3576 - 3000\)
M1 for \(\frac{\text{their interest}}{6 \times 3000} \times 100\) or \(3000 \times R \times 6 / 100 = 576\)
A1 for 3.2

(c) [5 marks]
M1 for multiplier 1.15 associated with 2022
M1 for multiplier 0.92 associated with 2023
M1 for equation \(1.15 \times 0.92 \times V = 264500\) or \(1.058V = 264500\)
M1 for \(V = \frac{264500}{1.058}\)
A1 for 250000
题目 10 · Structured Long Answer
11
(a) Simplify completely:
$$\frac{2x^2 - 5x - 3}{x^2 - 9}$$

(b) Solve the equation:
$$\frac{4}{2x - 1} - \frac{3}{x + 2} = 1$$

(c) Rearrange the formula to make \(t\) the subject:
$$w = \sqrt{\frac{t + 3}{2t - 1}}$$
查看答案详解

解题

(a)
Factorise the numerator:
\(2x^2 - 5x - 3 = (2x + 1)(x - 3)\)
Factorise the denominator:
\(x^2 - 9 = (x - 3)(x + 3)\)
Simplify the fraction:
\(\frac{(2x + 1)(x - 3)}{(x - 3)(x + 3)} = \frac{2x + 1}{x + 3}\)

(b)
Multiply by common denominator \((2x - 1)(x + 2)\):
\(4(x + 2) - 3(2x - 1) = (2x - 1)(x + 2)\)
\(4x + 8 - 6x + 3 = 2x^2 + 3x - 2\)
\(-2x + 11 = 2x^2 + 3x - 2\)
\(2x^2 + 5x - 13 = 0\)
Use the quadratic formula:
\(x = \frac{-5 \pm \sqrt{5^2 - 4(2)(-13)}}{2(2)} = \frac{-5 \pm \sqrt{129}}{4}\)
\(x \approx 1.59\) or \(x \approx -4.09\)

(c)
Square both sides:
\(w^2 = \frac{t + 3}{2t - 1}\)
Multiply by \(2t - 1\):
\(w^2(2t - 1) = t + 3\)
\(2t w^2 - w^2 = t + 3\)
Collect terms with \(t\):
\(2t w^2 - t = w^2 + 3\)
\(t(2w^2 - 1) = w^2 + 3\)
\(t = \frac{w^2 + 3}{2w^2 - 1}\)

评分标准

(a) [4 marks]
B1 for factorising the numerator \((2x + 1)(x - 3)\)
B1 for factorising the denominator \((x - 3)(x + 3)\)
M1 for dividing out common factor \((x - 3)\)
A1 for \(\frac{2x + 1}{x + 3}\) as final answer

(b) [4 marks]
M1 for common denominator on LHS or multiplying through by denominator
M1 for \(2x^2 + 5x - 13 = 0\) (or equivalent 3-term quadratic)
M1 for substituting their values into quadratic formula
A1 for 1.59 and -4.09

(c) [3 marks]
M1 for squaring both sides \(w^2 = \frac{t+3}{2t-1}\)
M1 for isolating terms with \(t\) on one side \(t(2w^2 - 1) = w^2 + 3\)
A1 for \(t = \frac{w^2 + 3}{2w^2 - 1}\)
题目 11 · Structured Long Answer
11
A solid toy is formed by joining a solid cone of radius \(r\) and height \(h\) to a solid cylinder of the same radius \(r\) and height \(2r\).
The total height of the toy is 15 cm.
The radius of the cylinder and the cone is 3 cm.

(a) Show that the height of the cone is 9 cm.

(b) Calculate the total volume of the toy. Leave your answer in terms of \(\pi\).

(c) Calculate the total surface area of the toy.
查看答案详解

解题

(a)
Height of the cylinder = \(2r = 2(3) = 6\) cm.
Height of the cone = \(\text{Total height} - \text{Height of cylinder} = 15 - 6 = 9\) cm.

(b)
\(V_{\text{cylinder}} = \pi r^2 (2r) = 2\pi r^3 = 2\pi (3)^3 = 54\pi\) cm\(^3\).
\(V_{\text{cone}} = \frac{1}{3} \pi r^2 h = \frac{1}{3} \pi (3)^2 (9) = 27\pi\) cm\(^3\).
\(V_{\text{total}} = 54\pi + 27\pi = 81\pi\) cm\(^3\).

(c)
Total surface area consists of:
1. Base of the cylinder: \(\pi r^2 = \pi (3)^2 = 9\pi\) cm\(^2\).
2. Curved surface area of the cylinder: \(2\pi r (2r) = 4\pi r^2 = 4\pi (3)^2 = 36\pi\) cm\(^2\).
3. Curved surface area of the cone: \(\pi r l\).
Find slant height \(l\):
\(l = \sqrt{r^2 + h^2} = \sqrt{3^2 + 9^2} = \sqrt{90} = 3\sqrt{10} \approx 9.4868\) cm.
\(\text{CSA}_{\text{cone}} = \pi \times 3 \times 9.4868 \approx 28.46\pi\) cm\(^2\).
\(\text{Total Surface Area} = 9\pi + 36\pi + 28.46\pi = 73.46\pi \approx 230.78 \approx 231\) cm\(^2\).

评分标准

(a) [2 marks]
M1 for finding height of cylinder = \(2 \times 3 = 6\)
A1 for showing \(15 - 6 = 9\)

(b) [3 marks]
M1 for volume of cylinder \(\pi \times 3^2 \times 6 = 54\pi\)
M1 for volume of cone \(\frac{1}{3} \pi \times 3^2 \times 9 = 27\pi\)
A1 for \(81\pi\)

(c) [6 marks]
M1 for area of circular base = \(9\pi\) or \(28.3\)
M1 for curved area of cylinder = \(36\pi\) or \(113.1\)
M1 for slant height of cone \(l = \sqrt{3^2 + 9^2}\)
A1 for slant height \(\approx 9.49\) or \(3\sqrt{10}\)
M1 for curved area of cone = \(\pi \times 3 \times 9.49\) (\(\approx 89.4\))
A1 for total surface area 231 (accept 230.7 to 231.2)
题目 12 · Structured Long Answer
11
In quadrilateral \(ABCD\):
\(AB = 7.5\) cm, \(BC = 6.2\) cm, and angle \(ABC = 112^\circ\).
\(CD = 14.5\) cm, and angle \(ACD = 38^\circ\).
Angle \(ADC\) is an acute angle.

(a) Calculate the length of \(AC\).

(b) Calculate angle \(ADC\).

(c) Calculate the area of the triangle \(ABC\).

(d) Calculate the shortest distance from \(B\) to \(AC\).
查看答案详解

解题

(a)
Using the Cosine Rule on triangle \(ABC\):
\(AC^2 = AB^2 + BC^2 - 2 \cdot AB \cdot BC \cdot \cos(ABC)\)
\(AC^2 = 7.5^2 + 6.2^2 - 2(7.5)(6.2)\cos(112^\circ)\)
\(AC^2 = 56.25 + 38.44 - 93 \cdot (-0.3746)\)
\(AC^2 = 94.69 + 34.838 = 129.528\)
\(AC \approx 11.38 \approx 11.4\) cm.

(b)
Using the Cosine Rule on triangle \(ACD\) to find \(AD\):
\(AD^2 = AC^2 + CD^2 - 2 \cdot AC \cdot CD \cdot \cos(ACD)\)
\(AD^2 = 129.528 + 14.5^2 - 2(11.381)(14.5)\cos(38^\circ)\)
\(AD^2 = 129.528 + 210.25 - 330.049 \times 0.7880\)
\(AD^2 = 339.778 - 260.079 = 79.699\)
\(AD \approx 8.927\) cm.
Now, find angle \(ADC\) using the Cosine Rule:
\(\cos(ADC) = \frac{AD^2 + CD^2 - AC^2}{2 \cdot AD \cdot CD}\)
\(\cos(ADC) = \frac{79.699 + 210.25 - 129.528}{2 \times 8.927 \times 14.5} = \frac{160.421}{258.883} \approx 0.6197\)
\(\text{Angle } ADC = \cos^{-1}(0.6197) \approx 51.7^\circ\).

(c)
\(\text{Area of triangle } ABC = \frac{1}{2} \cdot AB \cdot BC \cdot \sin(ABC)\)
\(\text{Area} = \frac{1}{2} \cdot 7.5 \cdot 6.2 \cdot \sin(112^\circ) = 23.25 \times 0.9272 \approx 21.6\) cm\(^2\).

(d)
\(\text{Area of triangle } ABC = \frac{1}{2} \cdot AC \cdot d\)
\(21.557 = \frac{1}{2} \cdot 11.381 \cdot d\)
\(d = \frac{2 \times 21.557}{11.381} \approx 3.79\) cm.

评分标准

(a) [3 marks]
M1 for implicit cosine rule formula: \(AC^2 = 7.5^2 + 6.2^2 - 2(7.5)(6.2)\cos(112^\circ)\)
A1 for \(AC^2 \approx 129.5\)
A1 for 11.4 (accept 11.38 to 11.4)

(b) [4 marks]
M1 for finding \(AD^2 = 11.38^2 + 14.5^2 - 2(11.38)(14.5)\cos(38^\circ)\)
A1 for \(AD \approx 8.93\)
M1 for \(\cos(ADC) = \frac{AD^2 + 14.5^2 - 11.38^2}{2 \times AD \times 14.5}\) or equivalent sine rule method
A1 for 51.7 (accept 51.68 to 51.75)

(c) [2 marks]
M1 for area formula: \(0.5 \times 7.5 \times 6.2 \times \sin(112^\circ)\)
A1 for 21.6 (accept 21.55 to 21.6)

(d) [2 marks]
M1 for \(0.5 \times 11.38 \times d = \text{their area in (c)}\)
A1 for 3.79 (accept 3.78 to 3.80)

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