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

Let the number of blue balls be X

So total number of balls = 5+X

P(probability of drawing a red ball from the bag) = 5/(5 + X)

P(probability of drawing a blue ball from the bag) = 3 5(5 + X) 

ATQ ,

5X +X² = 75+15X

X² - 10X+ -75 = 0

(x-15)(x+5) =0

So X ≠ -5

Therefore No. Of blue balls = 15