Question

A bag contain $4$ white balls and $3$ black balls. Two balls are drawn at random Find the probability that they are of the same colour.

Answer 1

Total number of drawing 2 balls out of 10balls
=$\frac{10\times (10-1)}{2}=45$
E= event of getting both balls of same colour
$\therefore$$n\left(E\right)=\frac{4\times (4-1)}{2}+\frac{3(3-1)}{2}$
=6+3=9
$P\left(E\right)=n\left(E\right)÷n\left(S\right)=\frac{9}{45}=\frac{1}{5}$
$\frac{1}{5}$