Question

Here are two adverts for cornflakes: 750g box Normal price £1.98 Buy one box, get 2nd box half price 500g box Normal price £1.75 Buy one box, get one free Which is the cheapest way to buy 1500g of cornflakes, A: two 750g boxes B: three 500g boxes? b) How much does it cost to buy 1500g of cornflakes, if you use the cheapest way?​

Answer 1

a) A: two 750g boxes.

b) £2.97

Explanation:

750g box:

• Normal price = £1.98
• Offer: Buy one box, get 2nd box half price.

500g box:

• Normal price = £1.75
• Offer: Buy one box, get one free.

Part a)

Cost of two 750g boxes:

`\implies 1.98+(1.98)/(2)=1.98+0.99=2.97`

Cost of three 500g boxes:

`\implies 1.75+1.75+0=3.50`

As 2.97 < 3.50, it is cheaper to buy two 750g boxes.

Part b)

It costs £2.97 to buy 1500g of cornflakes using the cheapest way.

Answer 2

Need 1500 g of cornflakes

Option one, 750 g × 2

The cost

• £1.98 + £(1.98/2) = £2.97

Option two, 500 g × 3

The cost

• £1.75 + 0 + £1.75 = £3.50

Option one is cheaper as £2.97 < £3.50