SOLUTION: there are 40 students in a class with 23 male students. what is the probability that two selected students are female?

Question 478671: there are 40 students in a class with 23 male students. what is the probability that two selected students are female?
Answer by Maths68(1474) (Show Source): You can put this solution on YOUR website!
Total Students = 40
Male =23
Female=(40-23)=17
Selecting 2 students out of 40 = nCr
=40C2
=40!/(40-2)! 2!
=40*39*38!/38! 2!
=40*39/ 2!
=20*39
=780 ways
Selecting 2 female out of 17 = nCr
=17C2
=17!/(17-2)!2!
=17*16*15!/(15)!2!
=17*16/2
=17*8
=136 ways
P(2 selected students are female)=136/780
P(2 selected students are female)=0.1743
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