A bag contains 5 white and 3 black balls. Two balls are drawn at random. The probability that the drawn balls are of different colours, is equal to

$\frac{2}{7}$ $\frac{15}{28}$ $\frac{3}{7}$ $\frac{4}{7}$

$\frac{15}{28}$

Drawn balls should be such that one of them is white and another is black. Total ways of drawing two balls $={ }^8 C_2=28$ Total number of favourable ways $={ }^5 C_1 . { }^3 C_1=15$ Thus, required probability $=\frac{15}{28}$