Best Buy Questions
What are Best Buy Questions?
Best buy questions involve deciding which product works out cheapest. As the products are given in differing quantities we need to do some maths before we can compare them.
We either need to make the quantities the same or the cost the same. For most questions it is normally easiest to make the quantities the same.
One option is to find the cost of one of the products using the unitary method (divide the cost by however many you have).
The other option is to find a common multiple of the products. In the example question we have the price of 4 toilet rolls and the price of 9 toilet rolls. We can compare them by finding a common multiple of 4 and 9 (36 rolls).
Best Buy Example Question (Edexcel Foundation June 2020, Paper 3, Question 15)
Here are the costs of the same type of batteries in two shops.
Shop A Pack of 4 batteries £1.60
Shop B Pack of 6 batteries £2.70
Harry needs to buy at least 30 batteries.
He assumes that he has to buy batteries in whole packs.
Harry wants to buy the batteries as cheaply as possible from the same shop.
Which shop should he buy the batteries from, shop A or shop B?
