A budget is the money you have to spend. Add up the prices of what you buy, then take the total away from the budget to find what is left. Include the cents. To see how many more things you can buy, use only the money left, and remember you can only buy whole items. When choosing items, check every total against the budget: you must not go over.
Explore this idea with maths tools
Maths you can move
Build 8 + 5
Tap two gold counters to fill the ten-frame.
8 in the frame + 5 waiting. The total stays the same.
Words to know
- budget
- the amount of money you can spend
- total
- all the prices added together
Worked examples
Mia has $20. Mia buys a kite for $7 and a hat for $9. How much money does Mia have left?
- 1.Total spent: $7 + $9 = $16.
- 2.Money left: $20 − $16 = $4.
= 4
Leo has $30. Leo buys a cap for $12 and a torch for $9.50. Stickers cost $2 a sheet. How many sheets can Leo buy with the money left?
- 1.Money left: $30 − $12 − $9.50 = $8.50.
- 2.4 sheets cost $8 and 5 would cost $10, which is too much.
= 4
Ava has $20 to spend on exactly two different items. Prices: kite $12.50, hat $11.20, torch $8.40, cap $6.30. What is the most Ava can spend without going over $20?
- 1.$12.50 + $6.30 = $18.80 fits, and $12.50 + $8.40 = $20.90 is too much.
- 2.$11.20 + $8.40 = $19.60 fits and is the closest to $20.
= 19.6
For parents
Method: Keep a running total
What to say: How much have we spent so far? How much is left?
Common mistakes:
- Answers with the total spent instead of the money left.
- Takes only one item away from the budget and forgets the other.
- Ignores the cents in the prices and subtracts only the whole dollars.
- Rounds the number of items up, as if part of an item could be paid for.
- Works out how many can be bought with the whole budget, forgetting what was already spent.
- Answers with the money left instead of how many more items it buys.
- Picks the pair closest to the budget even though it costs more than the budget.
- Picks the most expensive item first, then the best second item, and misses a better pair.