Maths s1-Help Needed!!

[ashutoshamatya]

In a MBS first year class, there are there sections each including 20 students. In first section there are 10 boys and 10 girls, in the second section there are 15 boys and 5 girls and, in the third section there are 12 boys and 8 girls. Five students are selected from each group to form a committee of 15 students. What is the probability that all 15 students selected are girls?

 

[ahmed t]

i have a way but i need to know the anser

 

[ashutoshamatya]

3.7*10^(-9)

 

[Nikesh]

its so simple..........
First find the total possible selection of 15 people i.e (20Cr5)^3 = 3.7*10^12 as we have to select five students from each class.....
Then find the possible combination of 15 girls, five from each class i.e 10Cr5 * 5Cr5 * 8Cr5 = 14112
now the probability that all 15 selected are girls = 14112 / 3.7 * 10^12
=3.7 * 10^(-9)

is it ok..................