Question

A bag contains 6 red balls and some blue balls. If the probability of drawing a blue ball from the bag is twice that of a red ball, find the number of blue balls in the bag.

Answer 1

Given: number of red balls = 6 

Let number of blue balls be x 

Total number of possible outcomes, n(S) = 6 + x 

Number of favorable outcomes = n(E)

∴ P(E) = \(\frac{n(E)}{n(S)}\)

P(blue ball) = 2P(red ball)

⇒ \(\frac{x}{x+6}\) = \(\frac{2\times6}{x+6}\)

⇒ x = 12 

∴ number of blue balls = 12