Hello -

For step one I would use the binomial table to add the results for 9 successes and 10 successes out of 10 for p=.8

P(9/10) = .268 + P(10/10)= .107

.268+.107= .375

Then for part 2 use the answer for part a as your monthly probability

In other words, the probability of 9 of 10 printers working each month is 0.375

Therefore the probability of 9 of 10 or better working 5 months in a row is...

(0.375)(0.375)(0.375)(0.375)(0.375) = (0.375)^5 = 0.0074

Kevin B.

10/15/19

Ashley P.

Thanks a lot for the clearer explanation!10/18/19

Ashley P.

Thanks a lot for the response! For part b, why do we simply multiply that values 5 times? Is there any theorem/law etc. behind that?10/15/19