A class consists of 55% boys and 45% girls. 25% of the class are boys and scored an A on the test, and 35% of the class are girls and scored an A on the test. If a student is chosen at random and is found to be a girl, what is the probability that the student scored an A?

Question

anonymous · Answer

(A).78, (B).51, (C).47, (D).37, (E).65

hoblos · Answer

if we have two events A and B
P(A/B) = P(A and B) / P(B)

hoblos · Answer

so let's suppose here 
A: the student scored an A
B: the student is girl

hoblos · Answer

what is P(B) ?

anonymous · Answer

Am i looking for a number?

hoblos · Answer

for a percentage

anonymous · Answer

.1575 i got this by multiplying .35(amount of girls who passed with an A) by .45(percentage of girls in class)?

hoblos · Answer

it's not multiplying, you must divide percentage of girls who passed with A over percentage of girls in class

anonymous · Answer

.777777777 which rounds to .78

hoblos · Answer

yes that's correct

anonymous · Answer

Thank you @hoblos !!

hoblos · Answer

any time :)

anonymous · Answer

Would you have time for another?

anonymous · Answer

The probability of a randomly selected employee of a company being male is 60%. The probability of the employee being less than 30 years old is 70%. If the probability of the employee being less than 30 years old given that the employee is a male is 40%, what is the probability that the employee is a male, given that the employee is less than 30 years old?

anonymous · Answer

Would i do this one just like the other?

hoblos · Answer

well here you have two steps to make
first you must calculate the probability that the employee is a male and is less than 30 years old

anonymous · Answer

I knew there was something different, but i think i'll push this question off till tomorrow. Thanks again!!

hoblos · Answer

okay, if you face a problem solving it you tag me again and i'll try to explain it to you :)

anonymous · Answer

Will do.(:

anonymous · Answer

@hoblos