Question

a bag contains 5 red balls and some blue balls if the probability of drawing a blue ball from the bag is thrice that of a red ball find the number of blue balls in the bag​

Answer 1

Answer

15

Explanation

Let the number of blue balls be 'b'

So, total number of balls in bag = (5 + b)

So, probability of drawing a blue ball = b/(5 + b)

And, probability of drawing a red ball = 5/(5 + b)

Given that probability of drawing blue ball = thrice the probability of drawing red ball

⇒ b/(5 + b) = 3 × 5/(5 + b)

cancelling the denominator because it's equal on both sides

⇒ b = 3 × 5

⇒ b = 15

So, the number of blue balls in the bag is 15.