Fire station able to get to fire in <=5 min abt 80% of time

[ally2009]

Hello, Need a bit of help here:

Fire station able to get to fire in five min or less about 80% of time. if this is so, find the pro that out of the next ten fire calls:

b) it takes five minutes or less for five or more of the calls

How would I approach this?

It there a formula I can use for this?

Thanks,
Ally

 

[galactus]

Re: able

This is a binomial probability.

Out of 10 cases, the probability 5 or more(up to 10) are answered on time given the probability of answering on time is .80

\(\displaystyle \sum_{k=5}^{10}C(10,k)(.80)^{k}(.20)^{10-k}\)