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probability prob?

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Junior | Next Rank: 30 Posts
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probability prob?

by d0nw0ng » Mon Oct 08, 2007 10:20 am
a school will choose 1 of 7 applicants to fill a position in the chem dept and 2 of 10 to fill 2 positions in physics dept. if none of the applicants is eligible for a position in both depts, how many different sets of 3 applicants are there to fill the 3 positions

a 42
b 70
c 140
d 165
e 315
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by arocks » Mon Oct 08, 2007 12:01 pm
7C1*10C2 = 315

Ans: E
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Junior | Next Rank: 30 Posts
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by d0nw0ng » Mon Oct 08, 2007 12:25 pm
thanks arock. can you tel me what C stands for?
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Junior | Next Rank: 30 Posts
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C is for "Choose"

by jcan-gmatter » Mon Oct 08, 2007 12:39 pm
Hey d0nw0ng,

The C is an indication that it is a combination type problem of the form:

nCr, where n = total number of choices AND r = number that we want to choose/select

In effect nCr means 7 Choose 1 or 10 Choose 2. Then we use the combination formula to identify the total # of ways that we can choose r from n.

Formula is: -

nCr = n! / (n-r)!r!
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Junior | Next Rank: 30 Posts
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by d0nw0ng » Mon Oct 08, 2007 12:41 pm
coo. thank you guys
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