South African Mathematics Olympiad First Round

Question

A shop has a special offer on pumpkins: "Buy one, get one at half price". For this offer, the average cost per pumpkin is the same as in (A) Two for the price of one (B) Three for the price of one (C) Three for the price of two (D) Four for the price of three (E) Five for the price of four

Accepted Answer

If you buy one item and get one at half price you are getting two items for the price of one and a half items. Since 2 : 112 is equivalent to 4 : 3, the average cost per item is the same as four items for the price of three.