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How many missiles should be fired?

i cannot figure out the answer for this. if u can, please help me. a missile is fired at target and the probability that the target is hit is 0.7. find how many missiles should be fired so that the probability that the target is hit at least once is greater than 0.995? thank you
Question asked by: thiliniiw

Asked on: 11 Jul 2010

OK so the probabilities you have are: 0.7 per hit and want to make sure greater than 0.995 in total.

Let's say you fire two. The probability both miss is 0.3 x 0.3, which is 0.09, so a 0.91 that one hits. Not enough.

With three is 0.3 x 0.3 x 0.3 = 0.027 so still not enough. Just keep on multiplying 0.3 x itself until you find which multiple is less than 0.005 and then you will have your answer.

By: knowitall
Replied at: 11 Jul 2010
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