Question

A shop promoting soap bars encourages you to ‘buy three get another one free’. If you want 2014 bars, what is the least number you have to pay for?

Answer 1

If you buy three bars of soap, you get one free.

In fact, you are actually getting four soaps. You need 2014 soaps, So:-

2014/4 = 503.5

So imagine that you get 503 soaps for free. That means, you need to buy in total 3×503 = 1509 soaps.

So if you buy 1509 soaps, you get 503 soaps for free and now you have in total 2012 soaps with you. So you have to buy two more.

So you need to pay for a minimum 1511 soaps to have 2014 in your hands.