i need to find out which of these is better value.

Question

£3.90 -9 pack of toilet rolls
or £2.50 6pack of toilet rolls.
i think its th £3.50 but i am finding it hard to show the working out.

Answer 1

convert each to cost per unit
1. £3.90/9 = £0.43 per roll
2. £2.50/6 = £0.42 per roll

so the second is "slightly" cheaper.