Question

A jar contains 24 marbles, some are green and others are blue. If a marble is drawn at random from the jar, the probability that it is green is $\frac{2}{3}$.
Find the number of blue balls in the jar.

Answer 1

Here, total number of outcomes = 24
Let there be x green marbles.
Then, the number of blue balls = 24 - x
Therefore favourable number of outcomes = x

$\therefore P\left(G\right)=\frac{x}{24}$

$ButP\left(G\right)=\frac{2}{3}$
$\Rightarrow \frac{x}{24}=\frac{2}{3}$
$\Rightarrow x=16$
Therefore number of green marbles are 16.
And number of blue marbles = 24 - x = 24 - 16 = 8