Question

There is a bag with only red marbles and blue marbles. The probability of randomly choosing a red marble is 7 12 . There are 72 marbles in total in the bag and each is equally likely to be chosen. Work out how many red marbles there must be.

Answer 1

63 red marbles.

Because the probability of drawing a red marble is 7/8, the number of red marbles = 7/8 * 72
= 7 * 9
= 63.