GCSE Maths Practice: best-value

Question 7 of 10

Different rice packs have different weights and prices. Use unit price to find the best value.

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\( \begin{array}{l} \text{Which pack of rice gives the best value for money?} \end{array} \)

Choose one option:

Divide the total cost by the weight to compare packs fairly.

Best Value Problems Using Weight

Best value questions are a common feature of GCSE Maths because they reflect real-life shopping decisions. Products such as rice, pasta, flour, and pet food are often sold in different pack sizes, making it difficult to decide which option offers the best value. Looking only at the total price can be misleading, as a larger pack usually costs more overall but may be cheaper when compared per kilogram.

The aim of best value problems is to help you compare options fairly by using a single, common unit. For products sold by weight, this unit is usually one kilogram.

The Unit Price Method

The most reliable method for solving best value questions is to calculate the unit price, which means the cost per kilogram.

  1. Check the weight of each option and convert grams to kilograms if needed.
  2. Divide the total price by the weight in kilograms.
  3. Compare the costs per kilogram.

The option with the lowest cost per kilogram represents the best value for money.

Worked Example

A shop sells bags of pasta:

  • 750 g for £1.50
  • 1 kg for £2.10
  • 2 kg for £3.90

Convert grams to kilograms, then calculate the cost per kilogram:

  • £1.50 ÷ 0.75 = £2.00 per kg
  • £2.10 ÷ 1 = £2.10 per kg
  • £3.90 ÷ 2 = £1.95 per kg

Comparing these values shows which pack offers the lowest unit price.

Another Example

Pet food is sold as:

  • 400 g for £0.88
  • 1 kg for £2.20
  • 3 kg for £6.30

After converting all weights to kilograms, divide the price by the weight to compare fairly.

Common Mistakes

  • Not converting units: Always convert grams to kilograms before dividing.
  • Comparing total prices: The cheapest pack overall may not be the best value.
  • Incorrect division: Always divide price by weight, not weight by price.

Real-Life Applications

Unit pricing is used in supermarkets to help customers compare products quickly. Shelf labels often display the cost per kilogram, allowing shoppers to see which option is better value at a glance. This skill is also useful when buying food in bulk, comparing offers, or planning a budget.

Understanding best value calculations helps you make smarter financial decisions and avoid misleading deals.

Frequently Asked Questions

Why do we use cost per kilogram?
It allows all options to be compared using the same amount.

What if two options have the same unit price?
They offer equal value, and either could be chosen.

Is this topic assessed in GCSE exams?
Yes. Best value by weight appears frequently on Foundation papers.

Study Tip

Whenever weights and prices appear together, calculate the unit price before choosing an answer.

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