Hello to all our lovely Grade 3 students!

Welcome to our lesson on "Money and Recording Income and Expenses." Did you know that we deal with money every single day? Whether it’s buying snacks, dropping coins into your piggy bank, or receiving pocket money from your parents, this lesson will help you become the smartest "Little Money Manager" around!

If numbers seem a bit tricky at first, don't worry! We’ll go through everything together, step by step. Are you ready? Let’s dive in!


1. Writing and Reading Amounts of Money

In Thailand, we use the units Baht and Satang. There is one golden rule you must always remember:

Important Point: \(100 \text{ Satang} = 1 \text{ Baht}\)

Using a "Decimal Point" (.) to Write Money

You’ve probably seen numbers with a dot in the middle, like 25.50 Baht. What does that mean? Let’s break it down simply:

  • Numbers before the dot: Represent the amount in Baht.
  • Numbers after the dot: Represent the amount in Satang (there will always be 2 digits).
  • Ending the sentence: We write the word Baht at the very end.

For example:
10.25 Baht is read as Ten Baht, Twenty-five Satang.
150.75 Baht is read as One hundred and fifty Baht, Seventy-five Satang.
5.00 Baht is read as Five Baht (if there is 00 after the dot, you don't need to say "zero satang").

Did you know? The Satang coins still in use today are the 25-satang and 50-satang coins, which you will often see at supermarkets or convenience stores.

Summary of this section: Before the dot is Baht, after the dot is Satang, and never forget that 100 Satang equals 1 Baht!


2. Comparing Amounts of Money

If you want to know which amount of money is larger, just follow these simple steps:

  1. Look at the "Baht" first: Compare the numbers before the dot. Whoever has more, that amount is larger immediately!
  2. If the "Baht" is the same, look at the "Satang": If the numbers before the dot are exactly the same, look at the digits after the dot. Whoever has more, that amount is larger.

Examples:
Between 50.25 Baht and 45.75 Baht -> 50 is greater than 45, so 50.25 Baht is more.
Between 20.50 Baht and 20.75 Baht -> The Baht are equal (20), but 75 Satang is more than 50 Satang, so 20.75 Baht is more.


3. Exchanging Money (It’s like playing a game!)

Exchanging money means swapping types of banknotes or coins for others that add up to the same total value.

  • One 100-Baht banknote can be exchanged for five 20-Baht banknotes (because \(20+20+20+20+20 = 100\)).
  • One 10-Baht coin can be exchanged for five 2-Baht coins.
  • One 50-Baht banknote can be exchanged for five 10-Baht coins.

Pro tip: Try taking the coins out of your piggy bank and sorting them into groups; it will help you understand how to add up money much faster!


4. Adding and Subtracting Money

Calculating money isn't hard at all, you just need to be very careful with the "decimal point."

Steps for adding/subtracting money:
  1. Always align the decimal points (this is the most important part!).
  2. Clearly separate the Satang part and the Baht part.
  3. Start adding or subtracting from the right (Satang) to the left (Baht).
  4. For addition: If the Satang total is 100 or more, carry it over to the "Baht" column (because 100 Satang = 1 Baht).
  5. For subtraction: If the top Satang number is smaller than the bottom number, "borrow" 1 Baht from the Baht column (which is equal to 100 Satang).

Common mistakes: Forgetting to write the decimal point or misaligning the columns, which leads to wrong answers. Always double-check your dots before starting!


5. Recording Income and Expenses

Keeping an income-expense record means noting down where you got your money (income) and what you spent it on (expenses) so you know how much money you have left (balance).

What does an income-expense table look like?

Usually, it has these columns:
1. Date: The day the transaction happened.
2. Description: Where the money came from or what you bought.
3. Income (Baht): The amount of money you received.
4. Expense (Baht): The amount of money you spent.
5. Balance (Baht): The money remaining at that time.

The Balance formula:
Previous Balance + New Income = Current Balance
Previous Balance - New Expense = Current Balance

Example of a record:
- March 1st: Mom gave me pocket money (Income) 50 Baht -> Balance 50 Baht.
- March 1st: Bought snacks (Expense) 15 Baht -> Balance 35 Baht (taking \(50 - 15\)).

Important Point: Keeping track of your income and expenses will help you learn to plan your spending and save money for the things you want to buy in the future!


Final Summary

Money isn't that difficult, is it? Just remember that "100 Satang equals 1 Baht" and when adding or subtracting, "keep the decimal points aligned." Once you have that down, money will be a piece of cake for you!

Try practicing by reading price tags when you go to the market with your parents. The more you practice, the better you'll get! Keep it up!