Posted by **Anshu** on Tuesday, August 27, 2013 at 4:26am.

Approximately 15% of the students in ST130

obtain A grade. If 3 students are selected at

random, find the probability that

a)all of them obtain A grade in ST130.

b)Exactly 2 obtain A grade in ST130.

c)at least one obtain A grade in ST130

- Math -
**Reiny**, Tuesday, August 27, 2013 at 8:16am
prob of A = .15

prob of notA = .85

a) prob all 3 to get A = (.15)^3 = .003375

b) exactly 2 A's = C(3,2) .15^2 (.85)

= .057375

c) at least one

= 1 - prob no A's

= 1 - .85^3 = .385875

or the long way:

prob oneA + prob 2 A's + prob 3 A'a

= C(3,1) (.15)(.85)^2 + C(3,2) (15)^2 (.85) + C(3,3) (.15)^3

= .325125 + .057375 + .003375

= .385875

## Answer This Question

## Related Questions

- Statistic - Out of 150 ST130 students in 2010, 52% passed. A sample of 30 ...
- Math Word Problem - Riding on a school bus are 20 students in ninth grade, 10 ...
- math - Mercy must obtain an average mark of at least 85 to get an A grade in her...
- Probability Math - A committee of four students will be selected from a list ...
- Math - Which is the best way to obtain a random sample when surveying a high ...
- MATH - Taylor surveys students in one grade level who own at least one pet. She ...
- math - Taylor surveys students in one grade level who own at least one pet. She ...
- MATH - there are 400 students at smith Elementary school 1/4 of the students are...
- 11th grade - The students of litchfield High school are in grades 9,10,11,12. Of...
- math - For a class of 43 students, for a certain test, the mean grade is 67 and ...

More Related Questions