# no. of bombs required to destroy : question

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• August 9th 2011, 04:51 AM
electroboy
no. of bombs required to destroy : question
please give me a clue for the following question..

There is 50% chance that any bomb may hit the target. Two direct hits are required to destroy the target completely. How many bombs must be dropped for 99% chance?

Thanks in advance....
• August 9th 2011, 07:19 AM
chisigma
Re: no. of bombs required to destroy : question
Quote:

Originally Posted by electroboy
please give me a clue for the following question..

There is 50% chance that any bomb may hit the target. Two direct hits are required to destroy the target completely. How many bombs must be dropped for 99% chance?

Thanks in advance....

The solution of the problem is the solution of the 'equation'...

$1-\sum_{k=0}^{1} \binom{n}{k}\ p^{k}\ (1-p)^{n-k} = .99$ (1)

... where $p=\frac{1}{2}$ and $n$ is the 'unknown quantity'...

Kind regards

$\chi$ $\sigma$