A bag contains 5 white, 7 red and 4 black balls. If four balls are drawn one by one with replacement, what is the probability that none is white?

Explanation

P( none is white ) `=P(0)={4} C_{0}(frac{3}{4})^{4-0}(frac{1}{4})^{0}=1 times(frac{3}{4})^{4} times 1=frac{81}{256}`