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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?

 Oct 22, 2019
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"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.

 Oct 23, 2019
edited by Alan  Oct 23, 2019

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