# Need help on probability question

• Oct 15th 2006, 07:28 PM
eureka
Need help on probability question
There are 5 men and 3 women in a room. Given probability for men with beard is 1/10.

a) find the probability that there are three men with beard and two with no beard.
Do i need to count three men with beard X two men with not beard? or only count for three men with beard?

b)if two people are selected randomly from the people in the room, what is the probabiliy that both of them are men with beard?

Any idea?
• Oct 15th 2006, 08:11 PM
ThePerfectHacker
Quote:

Originally Posted by eureka
There are 5 men and 3 women in a room. Given probability for men with beard is 1/10.

a) find the probability that there are three men with beard and two with no beard.
Find the probability of exactly three men having a bread (that implies other two doth not).
To do that use binomial probability,
5C3 (1/10)^3(9/10)^2

Quote:

b)if two people are selected randomly from the people in the room, what is the probabiliy that both of them are men with beard?
What is probability of selecting two men?
5C2/8C2
That means the probability of selecting two men.
What is probability of both having beards?
(1/10)(1/10)=1/100
Now multiply the two numbers you get for final answer.
• Oct 15th 2006, 08:44 PM
eureka
Probability
Hi ThePerfectHacker

Thanks for your help and sorry for double post, as i am new to forum and i would need to submit my work today.. therefore did wrong post... really sorry.

would need your clarification for second question, does that mean that;

5C2/8C2 = 5/14

and follow by 5/14 * 1/100 = 1/280

so the answer is 1/280, is that what you mean?

• Oct 15th 2006, 08:48 PM
ThePerfectHacker
Quote:

Originally Posted by eureka
Hi ThePerfectHacker

Thanks for your help and sorry for double post, as i am new to forum and i would need to submit my work today.. therefore did wrong post... really sorry.

would need your clarification for second question, does that mean that;

5C2/8C2 = 5/14

and follow by 5/14 * 1/100 = 1/280

so the answer is 1/280, is that what you mean?