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Best Buys

Best Buys

Best Buys uses proportion to compare two different proportions of the same item. Determine the unit cost for each of the two proportions, then determine which gives better value for money.

The unitary method can also be used to work with more appropriate values. Using values of 100s, 1000s, etc, may make calculations easier in some instance, such as working out the cost of 100g of a product.

Example 1

Value brand coffee costs £1.95 for 200g. A premium brand is on offer which is 300g for £2.89. Which works out to be cheaper?

Value brand: 200g costs £1.95, or 195p.

This is a proportion of 200g for 195p, change to 100g for 97.5p

Premium brand: 300g costs £2.89, or 289p.

This is a proportion of 300g for 289p, change to 100g for 96.3p

The premium brand is actually cheaper, as it costs 96.3p for each 100g.

Answer: Premium brand

Example 2

In a shop, safety razors for men cost £9.99 for a pack of four. Safety razors for women cost £7.99 for 3. Which are more expensive?

Men: 4 cost 999p, which is 4 for 999p or 1 for 249.75p

Women: 3 cost 799p, or 3 for 799p which is 1 for 266.33p

The unit cost of the razors for women are higher.

Answer: For women