Best buys
Objective. Compare unit prices to make justified choices.
- 1. Learn
- 2. Worked example
- 3. Practice
- 4. Feedback
- 5. Continue
Learn: the key idea
A best buy comparison finds which of two or more products offers better value for money, usually by calculating the unit price of each option. To find a unit price, divide the total cost by the total quantity, giving a price per gram, per litre or per item. For example, a 500 g bag costing £2 has a unit price of £0.004 per gram, while a 750 g bag costing £2.70 has a unit price of £0.0036 per gram, making the larger bag better value. Always compare prices using the same unit for a fair judgement.
Worked example
Compare these two best buys: a 400 g jar of coffee for £4.80, or a 600 g jar for £6.90. Which is better value?
- 1Find the unit price of the 400 g jar: 4.80÷400=£0.012 per gram.
- 2Find the unit price of the 600 g jar: 6.90÷600=£0.0115 per gram.
- 3Compare the two unit prices: 0.0115 is lower than 0.012.
- 4The jar with the lower unit price offers better value.
Answer: The 600 g jar is better value
Concept mastery
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Practice
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Start practisingCommon mistake. Pupils sometimes compare the total prices directly without considering the different quantities, wrongly assuming the cheaper total price is always the better buy. Always calculate a price per common unit before comparing.
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