SOLUTION: Problem: Grade___Students__>8 HRS.__<8 HRS. A_______13_______12_______1 B_______10_______8________2 C_______8________6________2 D_______9________2________7 F_______10_______1

Algebra ->  Probability-and-statistics -> SOLUTION: Problem: Grade___Students__>8 HRS.__<8 HRS. A_______13_______12_______1 B_______10_______8________2 C_______8________6________2 D_______9________2________7 F_______10_______1      Log On


   

Question 886408: Problem:
Grade___Students__>8 HRS.__<8 HRS.
A_______13_______12_______1
B_______10_______8________2
C_______8________6________2
D_______9________2________7
F_______10_______1________9
What is the probability of a randomly selected student having earned an F on the exam given they devoted more than 8 hours to studying for the exam?
a. 0.12
b. 0.03
c. 0.09
d. 0.17
I would need the answer (a,b, c or d) plus how to arrive at the answer so I can apply that to similar problems.
I tried this formula: P(A or B) = P(A) + P(B) – P(A and B) but it is not giving me any of the 4 possible answers. I am either using the wrong formula or plugging in the numbers wrong and cannot figure out which is the issue.
Thank you for your help!
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
29 students studied more than 8 hours
of those only one failed with an F
1/29=.034
which is answer b)

an aside :9 out of 10 who got an F studied less than 8 hours.