Compare two or more deals by unit price or a common amount, and justify which is better value. It is on Foundation and Higher, aimed at grade 3. Free questions with answers are on this page. Worked examples show each line before you try the questions.
Best-buy questions ask which pack is cheaper per unit. Find the cost of 1 g, 1 ml or 1 item for each offer, then compare. Alternatively, find how much of each you get per £1. Either comparison is fine — mixing them mid-question is not.
Special offers ('three for two', '20% extra') need the actual paid-for amount, not the sticker quantity. Show both unit costs to 3 s.f. or more, then state which is better value and by how much if asked. The cheaper pack is not always the one with the lower shelf price.
Compare the same amount of product, or compare price per unit. Do not compare '3 for £2' with '8 for £5' by looking at the pounds only — find pence per item (or grams per pound).
Objectives
Divide price by quantity.
Compare price per gram, or per tin, or per litre.
The lower unit price is the better value.
Key points
Work out a unit price (cost per item, per gram or per 100 g).
Compare deals by scaling both to the same amount.
Deal with offers like 'buy 2 get 1 free' or '3 for £2'.
Write a clear conclusion with numbers to back it up.
Worked examples
Example 1
Pack A has 2 tins for £6. Pack B has 4 tins for £8. Which pack is the better buy?
3 marks
Pack A: £6 ÷ 2 = £3 per tin.
Pack B: £8 ÷ 4 = £2 per tin.
Pack B has the lower price per tin, so it is the better buy.
Answer: Pack B
Common slips
Slip: Pack A: 2 ÷ £6 = 0.33 tins for £1. That is tins per pound. Divide the price by the number of tins to find the price of one tin.
Slip: Pack B: £8 − 4 = £4. Subtracting does not give the price of one tin. Divide the price by the number of tins.
Slip: Pack A has the lower total price, so it is the better buy. The total price ignores how many tins you get. Compare the price of one tin.
Example 2
Pack A has 4 tins for £12. Pack B has 2 tins for £8. Which pack is the better buy?
3 marks
Pack A: £12 ÷ 4 = £3 per tin.
Pack B: £8 ÷ 2 = £4 per tin.
Pack A has the lower price per tin, so it is the better buy.
Answer: Pack A
Common slips
Slip: Pack A: 4 ÷ £12 = 0.33 tins for £1. That is tins per pound. Divide the price by the number of tins to find the price of one tin.
Slip: Pack B: £8 − 2 = £6. Subtracting does not give the price of one tin. Divide the price by the number of tins.
Slip: Pack B has the lower total price, so it is the better buy. The total price ignores how many tins you get. Compare the price of one tin.
Example 3
Pack A has 3 tins for £12. Pack B has 6 tins for £18. Which pack is the better buy?
3 marks
Pack A: £12 ÷ 3 = £4 per tin.
Pack B: £18 ÷ 6 = £3 per tin.
Pack B has the lower price per tin, so it is the better buy.
Answer: Pack B
Common slips
Slip: Pack A: 3 ÷ £12 = 0.25 tins for £1. That is tins per pound. Divide the price by the number of tins to find the price of one tin.
Slip: Pack B: £18 − 6 = £12. Subtracting does not give the price of one tin. Divide the price by the number of tins.
Slip: Pack A has the lower total price, so it is the better buy. The total price ignores how many tins you get. Compare the price of one tin.
Questions and answers
GCSE Maths best buy questions questions and answers. Try each one, then open the answer. Easy questions come first.
Question 1 Easy2 marks
Pack A costs £6 for 3 tins. What is the price of one tin?
Show answer
Answer: 2
Divide the price by the number of tins.
The value is 2.
M1 — Divide the price by the number of tins.
A1 — Answer 2
Question 2 Easy2 marks
Pack A is £4 for 2. Pack B is £9 for 3. Which pack has the lower price per item, A or B?
Show answer
Answer: A
A costs £2 each.
B costs £3 each.
M1 — A costs £2 each.
A1 — Answer A
Question 3 Medium2 marks
A box of 12 costs £6. How many boxes do you get for £18?
Show answer
Answer: 3
One box costs £6.
Divide the money by that price.
M1 — One box costs £6.
A1 — Answer 3
Question 4 Medium2 marks
A is £6 for 2, B is £8 for 4, C is £15 for 5. Which is the best value, A, B or C?
Show answer
Answer: B
A is £3 each.
B is £2 each and C is £3 each.
M1 — A is £3 each.
A1 — Answer B
Question 5 Hard2 marks
A 500 g pack costs £8. 100 g is wasted. What is the price per 100 g of the part that is used?
Show answer
Answer: 2
400 g is used.
The price of 100 g is the pack price divided by 4.
M1 — 400 g is used.
A1 — Answer 2
Question 6 Hard2 marks
Deal A is 3 for £6. Deal B is 5 for £12. How much cheaper, in pounds, is one item on the better deal?
Show answer
Answer: 0.4
A is £2 each and B is £2.4 each.
The better deal is cheaper by £0.4.
M1 — A is £2 each and B is £2.4 each.
A1 — Answer 0.4
Question 7 Exam-style3 marks
A 500 g pack costs £12. 100 g is wasted. What is the price per 100 g of the part that is used?
Show answer
Answer: 3
400 g is used.
The price of 100 g is the pack price divided by 4.
M1 — 400 g is used.
M1 — The price of 100 g is the pack price divided by 4.
A1 — Answer 3
Common mistakes
Most lost marks on this topic are one slip.
Choosing the cheaper pack without looking at the size.
Compare the price of one unit.
Dividing quantity by price and then still treating the smaller number as better.
If you calculated quantity per pound, the larger number is better. Be consistent.
Comparing different units.
Use price per gram for both, or price per pack for both, not a mixture.
Spot the slip
The better buy is the offer with
the lower price per unit
the lower total price
the bigger pack
Show the slip
the lower price per unit A bigger pack can still be worse value.
Exam tips
A calculator is useful here. Show the calculation you typed, not only the final line.
If the question says “show that”, the result is given. The marks are for the steps that reach it.
The method is the same on AQA-style and Edexcel-style papers.
Always end with a sentence: 'X is better value because … per … is less than …'.
Work in pence to avoid decimal slips, then convert back if the question wants pounds.
Printable worksheet
The same questions are in a PDF you can print. Answers start on a later page.