Question

There are 7 students in a class: 5 boys and 2 girls. If the teacher picks a group of 4 at random, what is the probability that everyone in the group is a boy?

Answer 1

1/7

Explanation:

5C4 ÷ 7C4

= 5/35

= 1/7

Answer 2

probability that everyone in the group is a boy = 0.1428

Explanation:

Here we have , There are 7 students in a class: 5 boys and 2 girls. If the teacher picks a group of 4 at random, We need to find what is the probability that everyone in the group is a boy . Let's find out:

Initially we have , 7 students out of which 5 boys, so probability choosing first boy will be :

⇒
`(5)/(7)`

After this we are left with 6 students and 4 boys , so probability choosing second boy :

⇒
`(4)/(6)`

After this we are left with 5 students and 3 boys , so probability choosing third boy :

⇒
`(3)/(5)`

After this we are left with 4 students and 2 boys , so probability choosing fourth boy :

⇒
`(2)/(4)`

So, probability that everyone in the group is a boy =
`(5)/(7) ((4)/(6) ) ((3)/(5) ) ((2)/(4) )` =
`\frac {1} {7}`

probability that everyone in the group is a boy = 0.1428