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).
 Required number of ways |
= (7C3 x 6C2) + (7C4 x 6C1) + (7C5) | |||||||||||
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| = (525 + 210 + 21) | ||||||||||||
| = 756. |
Discussion:
137 comments Page 10 of 14.
Shay tee said:
1 decade ago
Okay. How are 7c3 and 7c4 both equal to 35?
Rampal said:
1 decade ago
Ya because they said to select at least 3 men which means we can select till 5.
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.
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?
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?
Sweety said:
1 decade ago
This method is ok but it will take much time to do in examination hall.
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.
Riya said:
1 decade ago
There are 4 types of permutation & its solved by diff formula. Which type is this?
Nishi Kant said:
1 decade ago
Here it is clearly given that we have to select so here we have to apply the combination rule and at-least three is given so we have to start from three and proceed further.
ANBU said:
1 decade ago
@Pankaj.
They asked at least 3 men not compulsory 3 men so 4men and 5 men is also possibility.
They asked at least 3 men not compulsory 3 men so 4men and 5 men is also possibility.
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