Understand the idea.
Ask what the item must do
A consumer chooses goods or services. Before buying, check two things: will it meet the need, and can you pay for it? A cheaper pack is not suitable if it contains too few of the things you need.
Compare fair choices
Compare what you can actually use, not just the size or appearance of a pack. Sometimes reusing, sharing or repairing meets the need without a new purchase. Explain the money effect using the given prices; do not guess extra facts about the items.
See the method in action.
Choose a suitable amount
You need 4 pencils and have 5 dollars. Pack A has 4 pencils for 4 dollars. Pack B has 2 pencils for 3 dollars. Which single pack meets both conditions?
Worked solution
- 1
Check whether each single pack has enough pencils.
Pack A has the four needed pencils; Pack B has only two.
- 2
Check Pack A against the budget.
Its four-dollar cost fits the five dollars available.
- 3
Find the money left after choosing A.
Pack A meets both conditions and leaves one dollar.
Pack A; it leaves 1 dollar.
Reuse can be a choice
A project needs a clean box. You already have a suitable clean box. A new one costs 3 dollars. Give one sensible choice and its money effect.
Worked solution
- 1
Check the box already available.
The story says this box is clean and suitable for the project.
- 2
Choose to reuse that box.
No new box is needed to meet the stated project requirement.
- 3
Compare with buying the new box.
Reusing keeps the three dollars that the new purchase would have cost.
Reuse the suitable box and keep the 3 dollars for another purpose.
Try it yourself.
Check your understanding
You need 2 erasers. A pack of 2 costs 3 dollars and a pack of 5 costs 6 dollars. Your budget is 4 dollars. Which pack fits?
Show answer & reasoning
The pack of 2.
The pack of two contains the two needed erasers and costs three dollars, which is within four dollars. The six-dollar pack costs more than the budget.
Keep practising
6 worksheet questions
Read the questions online
- You need a ruler. A suitable ruler costs 2 dollars and a toy costs 2 dollars. Which meets the stated need?
- You need 3 cups. Pack A has 3 cups for 4 dollars. Pack B has 2 cups for 3 dollars. Which single pack has enough cups?
- You have 5 dollars. An item costs 6 dollars. Does a bright sale sign make it fit your budget?
- You can reuse a suitable folder or buy a new one for 4 dollars. How much purchase money is kept by reusing it?
- You need 4 stickers. A pack of 4 costs 3 dollars. A pack of 8 costs 5 dollars. You have 3 dollars. Which fits the stated conditions?
- A friend chooses a 4-dollar notebook over a 3-dollar one because only the 4-dollar notebook has the page size their task needs. Is choosing the dearer one sensible if they have 5 dollars? Explain.
Read the worked solutions
- You need a ruler. A suitable ruler costs 2 dollars and a toy costs 2 dollars. Which meets the stated need?
Equal prices do not make the items equally useful for the need.
The ruler. - You need 3 cups. Pack A has 3 cups for 4 dollars. Pack B has 2 cups for 3 dollars. Which single pack has enough cups?
Three cups are needed; two are not enough.
Pack A. - You have 5 dollars. An item costs 6 dollars. Does a bright sale sign make it fit your budget?
The cost is still 1 dollar more than the money available.
No. - You can reuse a suitable folder or buy a new one for 4 dollars. How much purchase money is kept by reusing it?
Reusing the folder avoids the 4-dollar new purchase.
4 dollars. - You need 4 stickers. A pack of 4 costs 3 dollars. A pack of 8 costs 5 dollars. You have 3 dollars. Which fits the stated conditions?
It provides enough stickers and uses exactly the 3-dollar budget.
The pack of 4. - A friend chooses a 4-dollar notebook over a 3-dollar one because only the 4-dollar notebook has the page size their task needs. Is choosing the dearer one sensible if they have 5 dollars? Explain.
Suitability matters as well as price; dollar remains.
Yes. It meets the task and fits the budget.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Comparing prices; $1/$2 coins and notes; purchases; limited money and saving; needs/wants; consumer choices.
Official curriculum source ↗