Question

A box contains $7$ red balls, $8$ green balls, and $5$ white balls. A ball is drawn at random from the box. Find the probability that the ball is white.

Answer 1

We have,

Total number of balls in the box $=7+8+5=20$ balls

Total possible outcomes $=20=n\left(S\right)$

Event of drawing a white ball = E = number of white balls $=5$

So, $n\left(E\right)=5$

Hence, probability of drawing a white ball $=n\left(E\right)/n\left(S\right)=5/20=1/4$