Q14 of 47 Page 1

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

Let the no of black balls be 'x'


No of white balls = 15


Total no of balls = 15 + x


Now, we know that


Probability of an event


⇒ P(getting a white ball)


⇒ P(getting a black ball)


Given,


P(getting a black ball) = 3 × P(getting a white ball)



⇒ x = 45


Hence, No of black balls is 45.


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