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.
Solution:
Total number of marbles = 24
Let the total number of green marbles be x.
Then, total number of blue marbles = 24 − xb
$\mathrm{P}$ (getting a given marble) $=\frac{x}{24}$
According to the condition given in the question,
$\frac{x}{24}=\frac{2}{3}$
$x=16$
Therefore, total number of green marbles in the jar = 16
Hence, total number of blue marbles = 24 − x = 24 − 16 = 8