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?

probability that everyone in the group is a boy = 0.1428

Step-by-step 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 :

⇒

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

⇒

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

⇒

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

⇒

So, probability that everyone in the group is a boy = =

probability that everyone in the group is a boy = 0.1428

1/7

Step-by-step explanation:

5C4 ÷ 7C4

= 5/35

= 1/7

except a rational number. : )

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )