Question

A jar contains 24 marbles. Some of these are green and others are blue. If a marble is drawn at random from the jar, the probability that it is green is `2/3`. Find the number of blue marbles in the jar.

Answer 1

Total number of marbles = 24.

Let the number of blue marbles be x.

Then, the number of green marbles = 24 − x

∴ P(getting a green marble) =  `("Number of favourable outcomes")/"Number of all possible outcomes"`

`= (24-x)/24`

But, P (getting a green marble) = 2/3 (given)

`therefore (24-x)/24 = 2/3`

⇒ 3 (24 - x) = 48

⇒ 72 - 3x= 48

⇒ 3x = 24

⇒ x = 8

Thus, the number of blue marbles in the jar is 8.