When Trilisa takes pictures, they turn out with probability 1/5. She wants to take enough pictures so that the probability of at least one turning out is at least 3/4. How few pictures can she take to accomplish this?
+33616 "When Trilisa takes pictures, they turn out with probability 1/5. She wants to take enough pictures so that the probability of at least one turning out is at least 3/4. How few pictures can she take to accomplish this?"
The probability that a picture doesn't turn out well is 4/5. The probability that n pictures don't turn out well is (4/5)n. Hence the probability that at least one picture turns out well is 1- (4/5)n. Equate this to 3/4 and rearrange to find n.
