Aptitude - Permutation and Combination - Discussion
Discussion Forum : Permutation and Combination - General Questions (Q.No. 1)
1.
From a group of 7 men and 6 women, five persons are to be selected to form a committee so that at least 3 men are there on the committee. In how many ways can it be done?
Answer: Option
Explanation:
We may have (3 men and 2 women) or (4 men and 1 woman) or (5 men only).
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= (7C3 x 6C2) + (7C4 x 6C1) + (7C5) | |||||||||||
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= (525 + 210 + 21) | ||||||||||||
= 756. |
Discussion:
137 comments Page 5 of 14.
Shams said:
1 decade ago
@Riya.
This is a Problem of Combination, There is only one formula is applied that is,
nCr = n!/(n-r)!r!.
(3 men and 2 women).
For man, n=7 & r=3.
For women n=6 & r=2.
(7C3 x 6C2) = 7! / (7-3)! 3! = 7*6*5*4*3! /4*3*2*1*3! = 840/24.
= 35.
So using this formula proceed further steps to get the result.
This is a Problem of Combination, There is only one formula is applied that is,
nCr = n!/(n-r)!r!.
(3 men and 2 women).
For man, n=7 & r=3.
For women n=6 & r=2.
(7C3 x 6C2) = 7! / (7-3)! 3! = 7*6*5*4*3! /4*3*2*1*3! = 840/24.
= 35.
So using this formula proceed further steps to get the result.
Sweety said:
1 decade ago
This method is ok but it will take much time to do in examination hall.
Swetha said:
1 decade ago
@Divya as in que asked as at least 3 men should be available in a group so we can't take 5 women. right?
Sharon said:
1 decade ago
GUYS.
How do we analyse that whether permutation or combination has to be used here?
How do we analyse that whether permutation or combination has to be used here?
H G said:
1 decade ago
Permutations are used to find the number of arrangements and combinations are you used to find the number of different ways of groups.
Rampal said:
1 decade ago
Ya because they said to select at least 3 men which means we can select till 5.
Shay tee said:
1 decade ago
Okay. How are 7c3 and 7c4 both equal to 35?
Chithra said:
1 decade ago
Combination is nothing but we are going to select from a particular group. In permutation also we will select from group, after selecting we need to arrange it according to the given condition.
i.e.) Combination -> selection.
Permutation -> selection followed by arrangement.
i.e.) Combination -> selection.
Permutation -> selection followed by arrangement.
Krishan said:
1 decade ago
Anyone could explain why we used 7c2 in second step?
Priyanka Das said:
1 decade ago
7C2 means 2 men are selected from 7 men.
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