The idea, step by step
Make the goal clear
A useful goal says what an item must do, what matters about it, and how much money can be used. It may be replacing a broken item, buying hobby equipment or sharing a class resource.
Compare products that meet the goal. Check pack sizes, delivery and what is included. The smallest price label is not always the lowest total cost for the quantity needed.
Find a workable saving plan
Subtract current savings from the target price to find what is still needed. Divide by the weekly saving. If another part of a week is needed, allow the next whole week.
A calculation supports a choice but does not decide every preference. Explain the relevant cost, quantity and purpose. Another person can make a different reasonable choice for a stated reason.
A common trap
Choose the cheaper-looking pack without checking how many items are needed.
Instead: Compare the total price for the same useful quantity.
See the thinking
Reach a target
Ella wants a 46-dollar drawing set. She has 14 dollars and saves 8 dollars a week. How many weeks are needed?
- Need: dollars.
- Weeks: .
- Check: .
Compare equal quantities
The class needs 12 pencils. A pack of 6 costs 5 dollars; a pack of 12 costs 9 dollars. Which is cheaper for 12 pencils?
- Two small packs provide pencils.
- Small-pack cost: dollars.
- Large-pack cost: 9 dollars.
- dollar is saved.
Check your understanding
A game costs 29 dollars. You have 9 dollars and save 6 dollars a week. How many whole weeks are needed?
Show answer
4 weeks
Need 20 dollars. Three weeks give 18 dollars, too little. Four weeks give 24 dollars, enough.
Your turn
6 questions · 14 marks · Work at your own pace.
Read the questions online
- A goal costs 38 dollars and you have 17 dollars. How much more is needed?2 marks
- You need 24 more dollars and save 6 dollars weekly. How many weeks?2 marks
- A goal costs 50 dollars. You have 14 dollars and save 8 dollars weekly. How many whole weeks?3 marks
- You need 10 books. A pack of 5 costs 7 dollars; a pack of 10 costs 13 dollars. Choose the cheaper total and find the saving.2 marks
- Store A sells a ball for 18 dollars plus 5 dollars delivery. Store B sells the same ball for 22 dollars with free delivery. Which total is lower?2 marks
- A folder must lie flat across the width of a bag. It is 30 cm wide. Bag A is 25 cm wide and costs 15 dollars. Bag B is 35 cm wide and costs 20 dollars. Give a sensible choice.3 marks
Read the worked solutions
Equivalent correct methods earn the corresponding marks. Include units where asked.
- A goal costs 38 dollars and you have 17 dollars. How much more is needed?2 marks
.
21 dollars - You need 24 more dollars and save 6 dollars weekly. How many weeks?2 marks
.
4 weeks - A goal costs 50 dollars. You have 14 dollars and save 8 dollars weekly. How many whole weeks?3 marks
Need dollars.
Four weeks give 32 dollars, too little.
Five weeks give 40 dollars, enough.
5 weeks - You need 10 books. A pack of 5 costs 7 dollars; a pack of 10 costs 13 dollars. Choose the cheaper total and find the saving.2 marks
Two small packs cost dollars.
.
One pack of 10 saves 1 dollar. - Store A sells a ball for 18 dollars plus 5 dollars delivery. Store B sells the same ball for 22 dollars with free delivery. Which total is lower?2 marks
A: dollars.
B: 22 dollars.
.
Store B by 1 dollar. - A folder must lie flat across the width of a bag. It is 30 cm wide. Bag A is 25 cm wide and costs 15 dollars. Bag B is 35 cm wide and costs 20 dollars. Give a sensible choice.3 marks
Compare with 30 cm: and .
A cheaper bag that cannot fit the folder does not meet this goal.
Bag B fits the stated goal; Bag A is too narrow.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics 2026
Practical models; immediate/future financial plans; consumer goals; ethical/sustainable choices.
Official curriculum source ↗