Addition, subtraction & money
Money
Adding and subtracting money is just like adding and subtracting numbers, but you must take note of the units. This unit uses dollars ($) and cents (c), and a decimal point to show both in one amount.
The decimal point in money
There are 100 cents in 1 dollar. The number of dollars is written after the dollar sign ($) and before the decimal point. The number of cents is written after the decimal point. Example: $4 and 24c = $4.24. When you use the $ sign you do not need the c as well. Remember to write small cent amounts with a zero, so 5c is .05, giving $24.05.
Adding money to find totals
Add money the same way you add numbers, keeping the cents together and the dollars together. Take care with the units. Example: a coffee ($3.00) plus a soda ($1.10) plus a milkshake ($3.25) = $7.35.
Finding change by subtracting
The change is the money you have left after you pay: change = money paid - amount spent. Example: Riya pays for trainers with a $50 note and gets $17 change, so the trainers cost $50 - $17 = $33.
Worked examples
Using a decimal point
- There are $4 whole dollars — write them after the $ sign and before the point.
- There are 24 cents — write them after the point.
- You do not need to write the c as well as the $ sign.
Answer: $4 and 24c = $4.24
Total and change
- Sumi buys a pencil (18c) and an eraser (26c). Add: 18c + 26c = 44c.
- She has 50c, so subtract what she spent: 50c - 44c.
- The change is what is left.
Answer: She spends 44c and gets 6c change.
Finding a cost from the change
- Xiumin pays for a comic and gets some change back.
- The comic costs the money he had minus his change: $6.50 - $1.20.
- Keep the dollars and cents lined up.
Answer: The comic costs $5.30.
Where you see this in real life
- Working out the total cost of drinks at a cafe, then the change from a $10 note.
- Buying items at the school shop and finding how much change you have left.
- Finding the price of trainers or a jacket from the note you paid with and the change you got.
Key words
- Decimal point
- The dot that separates the dollars from the cents in an amount of money.
- Cents
- Small units of money; there are 100 cents in 1 dollar. Written after the decimal point.
- Dollars
- The whole units of money, written after the $ sign and before the decimal point.
- Change
- The money you get back after paying — the amount paid minus the amount spent.
- Spend
- To pay money for something.