GCSE Maths Practice: best-value

Question 5 of 10

Flour bags come in different sizes and prices. Use unit price to find the best value.

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\( \begin{array}{l} \text{Which flour bag offers the best value for money?} \end{array} \)

Choose one option:

When unit prices are close, avoid rounding until the end.

Higher GCSE Best Value with Close Unit Prices

At Higher tier GCSE Maths, best value questions are often designed so that the unit prices are very close together. This removes the possibility of guessing and forces accurate calculation. In real-life shopping situations, price differences between products are often small, so understanding how to compare unit prices precisely is an important skill.

In this question, flour bags are sold in different weights with prices that appear similar when viewed casually. A quick look might suggest that the largest bag is best value, but this assumption is not always correct. The only reliable way to decide is to calculate the cost per kilogram for each option.

The Core Method: Cost per Kilogram

For products sold by weight, the standard unit for comparison is the cost per kilogram.

  1. Check that all weights are measured in kilograms.
  2. Divide the total price by the weight.
  3. Compare the resulting unit prices.

The option with the lowest cost per kilogram offers the best value.

Worked Example

A supermarket sells bags of sugar as:

  • 1.2 kg for £1.68
  • 2 kg for £2.76
  • 750 g for £1.05

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

  • £1.68 ÷ 1.2 = £1.40 per kg
  • £2.76 ÷ 2 = £1.38 per kg
  • £1.05 ÷ 0.75 = £1.40 per kg

Comparing these values shows which option offers the lowest unit cost.

Another Higher-Tier Example

Rice is sold as:

  • 1.75 kg for £2.45
  • 2.5 kg for £3.50
  • 1 kg for £1.42

Dividing price by weight gives unit prices that are very close, so careful decimal work is essential.

Common Higher-Tier Mistakes

  • Rounding too early: Rounding during calculations can change which option appears cheapest.
  • Assuming bigger is better: Larger packs are not always better value.
  • Inaccurate division: Small calculation errors matter when unit prices are close.

Real-Life Applications

Supermarkets commonly use unit pricing labels to show cost per kilogram for products like flour, rice, sugar, and pet food. These labels help shoppers make quick comparisons when prices are very similar.

Understanding how to calculate unit prices yourself ensures you are not misled by packaging size or marketing.

Frequently Asked Questions

Why are the prices so close in Higher questions?
Higher-tier questions test accuracy and careful working rather than estimation.

Should I always use cost per kilogram?
Yes, when weights are given in kilograms or grams.

Is this common in GCSE Higher exams?
Yes. Best value questions with close decimal values appear regularly.

Exam Tip

Keep all decimal values until the final comparison, and double-check your division before choosing an answer.

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