A bag contains 6 white and 4 black balls. Two balls are drawn at random. Find the probability that they are of same colour.

A. 1

B. $$\frac{{2}}{{15}}$$

C. 3

D. $$\frac{{7}}{{15}}$$

Answer: Option D

Solution(By Examveda Team)

Number of ways two balls can be drawn from 10 balls (6 white +4 blacks)
$$ = {}^{10}{C_2} = \frac{{10 \times 9}}{{2 \times 1}} = 45$$
n(E) = Number of ways of drawing 2 balls from 6 white balls or 2 balls from 4 black balls
$$\eqalign{ & = {}^6{C_2} + {}^4{C_2} = 21 \cr & {\text{P}}\left( {\text{E}} \right) = \frac{{21}}{{45}} = \frac{7}{{15}} \cr} $$