# Thread: Help me with Math

1. ## Help me with Math

A study published in a consumer magazine indicated that when a husband and a wife shop for a car, the husband exerts the primary influence in the descision 70% of the time. Five couples who will be purchasing a car are selected at random. Determine the probability of:

a) In exactly two of the couples, the husband will exert the primary influence on the decision.

b) In all five couples, the husband will exert the primary influence on the decision.

I got for a).132 and for b).168 ...is this correct? I dont have an answer key to check.

2. @Ronith
Ana just told me on skype to tell you that you're right.

3. I got something different for a?

a) 0.7 x 0.7 x 0.3 x 0.3 x 0.3 = 0.01323

b is correct, though.

b) 0.7^5 = 0.16807

4. ## The Following User Says Thank You to Prince For This Useful Post:

Zachafer (05-25-2012)

5. Originally Posted by Prince
I got something different for a?

a) 0.7 x 0.7 x 0.3 x 0.3 x 0.3 = 0.01323

b is correct, though.

b) 0.7^5 = 0.16807
Both are correct. For a), you get the answer by using binomial probability density function. (5C2) * (.7^2) * (.3^3) = .132

6. ## The Following User Says Thank You to bamag For This Useful Post:

Prince (05-26-2012)

7. Originally Posted by bamag
Both are correct. For a), you get the answer by using binomial probability density function. (5C2) * (.7^2) * (.3^3) = .132
Ah, of course. Because it doesn't state which two couples.

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•