2 finding probability problems

Hello,

I've been re-working two problems since yesterday, and have been getting the same (wrong) result every time. Here are the problems:

The probability that a person in the US has type B+ blood is 9%. Five unrelated people in the US are selected at random.

a) Find the probability that all 5 have type B+ blood.

Here, I would convert 9% to .09. Then, $\displaystyle .09 * .09 * .09 * .09 * .09 = .000006 $

**HOWEVER:** the answer key says it is .0000059

b) Find the probability that none of the five types have type B+ blood.

$\displaystyle 1 - .000006 = .999994 $

then

$\displaystyle .999994 * .999994 * .999994 * .999994 * .999994 = .99997 $

HOWEVER: the answer key says it is .624

*c) Find the probability that at least one of the five has type B+ blood.*

$\displaystyle 1 - .99997 = .00003 $

**HOWEVER: **the answer key says it is .376

The second problem confused me from the get-go. Would you mind giving me a hint on how to start it?

*A distribution center receives shipments of a product from 3 different factories in the following quantities: 50, 35, and 25. Three times a product is selected at random, each time without replacement. Find the probability that:*

*a) All three products came from the third factory?*

*b) None of the three products came from the third factory?*

Thanks in advance!

Re: 2 finding probability problems

Quote:

Originally Posted by

**m58** Hello,

I've been re-working two problems since yesterday, and have been getting the same (wrong) result every time. Here are the problems:

The probability that a person in the US has type B+ blood is 9%. Five unrelated people in the US are selected at random.

a) Find the probability that all 5 have type B+ blood.

Here, I would convert 9% to .09. Then, $\displaystyle .09 * .09 * .09 * .09 * .09 = .000006 $

**HOWEVER:** the answer key says it is .0000059

b) Find the probability that none of the five types have type B+ blood.

$\displaystyle 1 - .000006 = .999994 $

then

$\displaystyle .999994 * .999994 * .999994 * .999994 * .999994 = .99997 $

HOWEVER: the answer key says it is .624

*c) Find the probability that at least one of the five has type B+ blood.*

$\displaystyle 1 - .99997 = .00003 $

**HOWEVER: **the answer key says it is .376

$\displaystyle (.09)^5=0.0000059049$

$\displaystyle (.91)^5=0.6240321451$

$\displaystyle 1-(.91)^5=0.3759678549$