A bag contains 8 white balls and some black ones .if a ball is picked at random the probability that it is white is 0.2 .Find the number of black balls
number of black balls ---- x
8/(x+8) = .2
.2x + 1.6 = 8
.2x = 6.4
x = 32 <----- number of black balls
n is Total number
0.2 n = 8
n = 8/.2 = 40
40 - 8 white = 32 black