Let the number of white balls be n
The number of red balls = 8
Now, the probability of drawing a white ball =
The probability of drawing a red ball =
Since Pr(White ball) = x Pr(Red ball)
∴=×
= =
∴n=4
Number of white balls = 4
The possible number of outcomes = n + 8 = 4 + 8 = 12
Pr(Red ball and White ball) = Pr(Red ball) x Pr(White ball)
Pr(Red ball) =
Pr(Red ball) =
Pr(Red ball and white ball) = ×
∴Pr(Red ball and white ball) =