Answer :

Solution :

Number of blue balls = 15, Number of black balls = 45

Total number of balls = 15 + 45 = 60 balls

Balls are drawn from the box at random without replacement.

The probability of drawing first blue ball and second black ball is;

$P(E)=\frac{{15}_{C_1}}{{60}_{C_1}}\times \frac{{45}_{C_1}}{{59}_{C_1}}$

$P(E)=\frac{15\times 45}{60\times 59}$

$P(E)=\frac{45}{236}$