Question

A bag contains 15 white balls and some black balls. If the probability of drawing a black ball is thrice that of a white ball, find the number of black balls in the bag. Select the correct answer from above options

Answer 1

Number of white balls in a bag = 15 Suppose the number of black balls in the bag = x Total number of balls in the bag = 15 + x P(white ball) `=(15)/(15+x)` P(black ball) `=(x)/(15+x)` `"Now, "P(black ball) = 3P (white ball)" "(given)` `rArr" "(x)/(15+x)=3xx(15)/(15+x) rArr" "x=45` Therefore, the number of black balls in the bag are 45.