Pack A: 4 apples for £2. Pack B: 6 apples for £3. Which is better value?
Find cost per apple.
Pack A = £0.50 each, Pack B = £0.50 each → same value.
Best Value
Best value involves comparing prices to decide which option gives the most for the least cost. In GCSE Maths, this often requires calculating unit prices and making fair comparisons between different quantities using unit conversions.
Overview
Best value questions ask you to compare prices fairly.
The safest method is to work out the cost per 1 unit, such as cost per item, per kg, per 100 g or per litre.
\( \text{Unit cost} = \frac{\text{total cost}}{\text{number of units}} \)
Once both options are converted to the same unit, you can compare them directly. The lowest unit cost gives the best value.
What you should understand after this topic
- Understand what best value means
- Compare prices fairly
- Calculate cost per unit
- Handle different pack sizes
- Explain which option gives better value
Key Definitions
Best Value
The option that gives the lowest cost for the same amount.
Unit Cost
The price for one unit, such as one item, one kg or one litre.
Equivalent Comparison
Comparing options only after converting them to the same unit.
Offer
A deal such as “3 for £5” or “20% extra free”.
Per Unit
For each one of something.
Value for Money
How good a deal is compared with what you get.
Key Rules
Compare like with like
Use the same unit before deciding.
Find unit cost
Divide price by quantity.
Lowest unit cost wins
The smaller cost per unit is better value.
Watch the units carefully
Convert g to kg or ml to litres if needed.
Quick Comparison Methods
Per 1 item
Useful for packs of sweets, pens or tickets.
Per 100 g
Useful for food and smaller packs.
Per 1 kg
Useful for large masses.
Per 1 litre
Useful for drinks and liquids.
How to Solve
What does best value mean?
Best value means finding which option costs less for the same amount. You should not just look at the total price, because a larger price may still be better value if you get more for it.
Exam tip: Always compare like-for-like (same quantity or unit).
Main idea
Always convert each option to the same unit before comparing.
Step 1: Identify what is being compared
You might be comparing:
Why this matters: You cannot compare prices unless the quantities are understood.
- different numbers of items
- different masses
- different volumes
- special offers
Step 2: Choose one common unit
Convert both options to the same unit, for example:
1 item, 100 g, 1 kg, 100 ml or 1 litre
This often involves units and conversions before comparing.
Step 3: Find the unit cost
Divide the cost by the quantity to find the cost per unit.
\( \text{Unit cost} = \frac{\text{cost}}{\text{quantity}} \)
Exam tip: Always show your working when calculating unit cost.
Converting units when needed
Mass
\(1000\text{ g} = 1\text{ kg}\)
Volume
\(1000\text{ ml} = 1\text{ litre}\)
Money
\(100\text{ p} = £1\)
Advice
Make the units match before comparing.
Example Questions
Edexcel
Exam-style questions inspired by Edexcel GCSE Mathematics, focusing on comparing prices to determine the best value.
Edexcel
A 500 g bag of rice costs £1.80. A 1 kg bag costs £3.20. Which offers the best value?
Edexcel
A pack of 6 bottles of water costs £2.40. A pack of 10 bottles costs £3.50. Which pack is the best value?
Edexcel
A 750 g box of cereal costs £2.70. A 1.2 kg box costs £4.20. Determine which is the best value.
Edexcel
A 2-litre bottle of juice costs £3.60. A 1.5-litre bottle costs £2.55. Which is the better buy?
Edexcel
A car travels 420 miles using 35 litres of fuel. Another car travels 360 miles using 27 litres. Which car offers better fuel efficiency?
AQA
Exam-style questions based on the AQA GCSE Mathematics specification, emphasising unit rates and real-life decision-making.
AQA
A 12-pack of pencils costs £3.60. A 20-pack costs £5.00. Which offers the best value?
AQA
A 250 g jar of coffee costs £3.25. A 400 g jar costs £4.80. Which is the best value?
AQA
A phone contract costs £18 per month for 5 GB of data. Another costs £25 per month for 10 GB. Which offers the best value per gigabyte?
AQA
A 3-metre roll of ribbon costs £2.40. A 5-metre roll costs £3.75. Which is the better buy?
AQA
Explain how unit pricing helps determine the best value.
OCR
Exam-style questions aligned with OCR GCSE Mathematics, focusing on reasoning, unit comparison, and multi-step best-value problems.
OCR
A 6-pack of yoghurt costs £2.10. A 10-pack costs £3.80. Which is the best value?
OCR
A gym charges £45 for 6 sessions or £80 for 12 sessions. Which option offers the best value per session?
OCR
A 1.5 kg bag of dog food costs £4.50. A 4 kg bag costs £11.20. Which is the best value?
OCR
A printer uses two types of ink cartridges. Cartridge A prints 400 pages for £12, and Cartridge B prints 650 pages for £18. Which offers the best value?
OCR
Describe the steps required to determine which of two products offers the best value.
Exam Checklist
Step 1
Make sure both options are in the same unit.
Step 2
Work out the cost per unit for each option.
Step 3
Compare the unit costs carefully.
Step 4
State clearly which option is best value and why.
Most common exam mistakes
Price mistake
Choosing the lower total price without comparing amount.
Unit mistake
Comparing grams with kilograms or ml with litres directly.
Division mistake
Using the wrong quantity when working out unit cost.
Conclusion mistake
Not writing a final sentence saying which one is best value.
Common Mistakes
These are common mistakes students make when solving best value problems in GCSE Maths.
Comparing total prices only
Incorrect
A student chooses the cheaper product without considering the quantity.
Correct
Best value depends on unit cost, not total price. Always compare price per unit, such as price per kg or per item.
Not converting to the same unit
Incorrect
A student compares 500g with 1kg without converting.
Correct
All quantities must be in the same unit before comparing. For example, convert 1kg to 1000g to make a fair comparison.
Rounding too early
Incorrect
A student rounds unit prices before finishing the calculation.
Correct
Avoid rounding until the final answer. Early rounding can lead to incorrect comparisons between options.
Assuming bigger is always better value
Incorrect
A student chooses the larger pack without checking the cost per unit.
Correct
A larger pack is not always better value. Always calculate the unit price to decide which option is cheaper.
Mixing units incorrectly
Incorrect
A student compares grams with kilograms or millilitres with litres without converting.
Correct
Make sure all measurements use the same unit before comparing. Common conversions include 1kg = 1000g and 1L = 1000mL.
Try It Yourself
Practise comparing prices to determine the best value for money.
Foundation
Foundation Practice
Compare simple prices using unit cost.
A pack of 5 pens costs £10. What is the cost per pen?
Divide total cost by number of pens.
£10 ÷ 5 = £2 per pen.
Pack A: 6 yoghurts for £3. Pack B: 10 yoghurts for £4. Which is better value?
Compare cost per yoghurt.
A = £0.50 each, B = £0.40 each → Pack B is better.
A 2 kg bag of rice costs £4. What is the cost per kg?
Divide by 2.
£4 ÷ 2 = £2 per kg.
Which is better value: 500 g for £2 or 1 kg for £3?
Convert to cost per kg.
500 g = £4/kg, 1 kg = £3/kg → 1 kg is better.
A bottle contains 750 ml and costs £3. What is the cost per 250 ml?
750 ml ÷ 3 = 250 ml.
£3 ÷ 3 = £1 per 250 ml.
Pack A: 3 for £1.50. Pack B: 5 for £2. Which is better value?
Find cost per item.
A = £0.50, B = £0.40 → Pack B is better.
A 6-pack costs £3. What is the cost per item?
Divide 3 by 6.
£3 ÷ 6 = £0.50.
A student says the larger pack is always better value. Why is this wrong?
Think unit price.
You must compare unit cost, not total size.
A 1 litre bottle costs £2. What is the cost per 100 ml?
1 litre = 1000 ml.
£2 ÷ 10 = £0.20 per 100 ml.
Higher
Higher Practice
Solve best value problems involving unit conversions and multi-step comparisons.
Pack A: 750 g for £2.40. Pack B: 1.2 kg for £3.60. Which is better value?
Convert both to cost per kg.
A = £3.20/kg, B = £3.00/kg → Pack B is better.
A 300 g bar costs £1.80. Find the cost per 100 g.
Divide into 3 parts.
£1.80 ÷ 3 = £0.60 per 100 g.
Option A: 2 for £3. Option B: 5 for £7. Which is better value?
Compare unit price.
A = £1.50 each, B = £1.40 each → Option B is better.
A 1.5 litre drink costs £3. What is the cost per litre?
Divide by 1.5.
£3 ÷ 1.5 = £2 per litre.
Which is better value: 400 g for £1.20 or 1 kg for £3?
Convert both to per kg.
400 g = £3/kg, 1 kg = £3 → same value (trick!).
A 2.5 kg bag costs £5. Find the cost per 500 g.
2.5 kg = 2500 g.
500 g is 1/5 → £5 ÷ 5 = £1.
A student compares £4 for 8 items and £5 for 12 items and chooses £4 as cheaper. What is the mistake?
Think unit price.
You must compare cost per item, not total cost.
A 900 ml bottle costs £2.70. Find the cost per litre.
900 ml = 0.9 litres.
£2.70 ÷ 0.9 = £3 per litre.
Which is better value: 3 for £2 or 7 for £5?
Compare cost per item.
3 for £2 = £0.67, 7 for £5 = £0.71 → first is better.
A 1.8 kg bag costs £4.50. Find the cost per kg.
Divide 4.5 by 1.8.
£4.50 ÷ 1.8 = £2.50 per kg.
Games
Practise this topic with interactive games.
Games coming soon.