On average, a shooter can hit his target one time in four. If he fires 4 shots in a row, what is the probability that he will hit his target?
probability that he will not hit on a given shot = 3/4
probability that he will miss 4 times in a row
= (3/4)^4 = 81/256
so
probability that he will hit = 1 - 81/256
= 175/256 or about .684