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 42 red marbles in the bag and each is equally likely to be chosen work out how many marbles there must be

Answer 1

72

Explanation:

Given that:

P(Red) = Probability of randomly choosing a red

Probability of randomly choosing a red = 7/12

Number of red marbles = 42

The number of marbles in the bag :

P(Red) = number of red marbles / total number of marbles

Total number of marbles = (red marbles + blue marbles)

P(red) = 7/ 12 ;number of red = 42

P(Red) = number of red marbles / total number of marbles

Let:

x = total number of marbles

7/12 = 42 / x

(7/ 12)x = 42

7x / 12 = 42

7x = 12 * 42

7x = 504

x = 504 / 7

x = 72