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## #1 2018-02-24 12:12:48

Hannibal lecter
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Registered: 2016-02-11
Posts: 225
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A university committee should have 5 members. There are 5 candidates from the computer department, and 10 candidates from the math dept.
a) Find the probability of event  that 2 members would be from computer and 3 from math.
b) Is there a possibility that all the members are from math
c) Find the possibility that there is at least 1 person from computer

Wisdom is a tree which grows in the heart and fruits on the tongue

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## #2 2018-02-24 21:31:13

bob bundy
Registered: 2010-06-20
Posts: 8,462

### Re: important question about Probability

hi Hannibal lecter

A university committee should have 5 members. There are 5 candidates from the computer department, and 10 candidates from the math dept.
a) Find the probability of event  that 2 members would be from computer and 3 from math.
b) Is there a possibility that all the members are from math
c) Find the possibility that there is at least 1 person from computer

For (a) you need to calculate the probability of 2 from 5 (computer) and the probability of 3 from 10 (mathematics) and then put these together into a single probability.

I'll start you off with this:

P(2 from computers) = 5 / 15 x 4 / 14

But the same result can occur in 2 ways: eg. C1 followed by C2 or C2 followed by C1.  So you're in danger of counting the same result twice.  We avoid this by dividing by 2

P(2 from computers) = 5 / 15 x 4 / 14 ÷ 2

Then for the maths members you start with 10 / 13 and then continue for two more members.  This time to avoid repetitions you need to divide by 6 as

M1M2M3, M1M3M2, M2M1M3, M2M3M1, M3M1M2, M3M2M1 all give the same three maths members.

Please have a go at finishing this off and post your working.  I'll check it for you.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob Bundy

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## #3 2018-03-09 06:05:28

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: important question about Probability

from where did you get the number  4 / 14 ???
and why didn't you use Combinations Or  Permutations rules?
I'm so confused I can't imagine this

how could you  avoid repetitions by just divide by 2 or 6!!! isn't there something called combinations  without repetition or Permutations  without repetition

Last edited by Hannibal lecter (2018-03-09 06:09:36)

Wisdom is a tree which grows in the heart and fruits on the tongue

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## #4 2018-03-09 06:41:02

Hannibal lecter
Member
Registered: 2016-02-11
Posts: 225
Website

### Re: important question about Probability

and that the solution of the teacher note that the last number I think not 0.3996 it's 0.1721

anyway please see his solution :-

Wisdom is a tree which grows in the heart and fruits on the tongue

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