Question

A box contain some black balls and 30 white balls .If the probability of drawing a

black ball is two - fifth of a white ball. Find the number of black balls in the box.​

Answer 1

Step-by-step explanation:

No. of white balls = 30

No. of black balls = x (say)

Total no. of balls = 30+x

Given : Probability of drawing a black ball, i.e.,

P(B) = 2/5 of P(W).

= x /30+x = 2/5 of 30/30+x

= x/30+x = 12/30+x

= x = 12

Hence, the no. of black balls = 12.