Averages: แบบฝึกหัด

A runner recorded the daily running time for 4 days: \(42\) minutes, \(48\) minutes, \(53\) minutes, and \(57\) minutes.
What was the runner's average daily running time?

The average of \(4\) numbers is \(20\). Three of the numbers are \(15, 22,\) and \(18\). What is the fourth number?

The average age of a group of \(12\) people is \(25\) years. When a new person joins the group, the average age of all the people decreases by \(1\) year. How old is the person who joined the group?

A bar chart shows the number of books read by four students in a month: Tom read \(5\) books, Mary read \(7\) books, John read \(3\) books, and Lily read \(9\) books. What is the average number of books read by these four students?

The average height of three plants is \(12.4\text{ cm}\). Two of the plants have heights of \(10.5\text{ cm}\) and \(13.2\text{ cm}\). What is the height of the third plant?

A runner completed four practice laps in \(68\text{ s}\), \(72\text{ s}\), \(70\text{ s}\), and \(74\text{ s}\). What was his average time per lap in seconds?

The average score of 5 students in a quiz was $$70$$. After a re-evaluation, one student's score was increased by $$10$$ marks. What is the new average score of the 5 students?

The average score of $$4$$ quizzes was $$75$$. If a new quiz was taken and the score was $$90$$, what is the new average score for all $$5$$ quizzes?

The weights of 4 parcels in a delivery van are recorded as follows: \( 3.2\text{ kg} \), \( 4.5\text{ kg} \), \( 3.8\text{ kg} \), and \( 4.1\text{ kg} \).

a) Find the total weight of the 4 parcels.
b) Calculate the average weight of these 4 parcels.
c) If a 5th parcel weighing \( 6.4\text{ kg} \) is added to the van, what is the new total weight of all 5 parcels?
d) What is the new average weight of all 5 parcels?

A baker prepares pastries. For the first $$3$$ hours, he bakes an average of $$45$$ pastries per hour. In the next $$2$$ hours, he bakes $$30$$ pastries in the first hour and $$50$$ pastries in the second hour. What is the average number of pastries he baked per hour over these $$5$$ hours?