Question

A box contains 8 white balls, 7 black balls, & 2 red balls.

a) how many red balls must be added to the box so that the probability of drawing a red ball is 8/9
b)how many black balls must be added to the original box so that the probability of drawing a white ball is 1/9?

Answer 1

a) 118

b) 55

Explanation:

a) Originally, there are 2 red balls and a total of 17 balls.

8/9 = (2 + x) / (17 + x)

8 (17 + x) = 9 (2 + x)

136 + 8x = 18 + 9x

x = 118

b) Originally, there are 8 white balls and a total of 17 balls.

1/9 = 8 / (17 + x)

17 + x = 72

x = 55