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) | |||||||||||
|
||||||||||||
|
||||||||||||
| = (525 + 210 + 21) | ||||||||||||
| = 756. |
Discussion:
137 comments Page 6 of 14.
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.
Ali said:
8 years ago
@Harsh.
I think we need to multiply so that we get the total number of ways we can choose 3 men from a total of 13 men and women.
I think we need to multiply so that we get the total number of ways we can choose 3 men from a total of 13 men and women.
Sake said:
4 years ago
Why can't we do it like this,
Total ways = at least 3 men + not men.
i.e not men = 6c5.
Total ways= 13c5.
therefore,
13c5 - 6c5.
Total ways = at least 3 men + not men.
i.e not men = 6c5.
Total ways= 13c5.
therefore,
13c5 - 6c5.
(3)
Vivacity said:
1 decade ago
@leo: It can be A or B or C. The basic rules of permutations so we have to add them up A+B+C...where A,B,C refers to the terms.
Sujit said:
1 decade ago
Permutation is used when asked to find number of arrangement and Combination is used to find number of ways of combination.
Harsh said:
8 years ago
It's correct that we select 3 men from 7 and 2 women from 6. But why do we need to multiply it to get total no of ways?
Aryabhatt said:
8 years ago
Why don't we apply permutation after getting the answer 756 to get the number of ways those 5 persons can be arranged?
Abhishek Singh said:
6 months ago
3 men & 2 woman = 7C3 * 5C2 = 525.
4 men & 1 woman = 7C4 * 5C1 = 210.
5 men = 7C5 = 21.
So, the answer is 756.
4 men & 1 woman = 7C4 * 5C1 = 210.
5 men = 7C5 = 21.
So, the answer is 756.
(4)
Kanchan Srivastava said:
1 decade ago
nCr = nCn-r
and
7c4 = 35,
6c2= 15
I am unable to get it and how came
7c4 = 35 or 6c2= 15
Please explain it.
and
7c4 = 35,
6c2= 15
I am unable to get it and how came
7c4 = 35 or 6c2= 15
Please explain it.
Mayur said:
1 decade ago
Why only that formula used in 7c4 n 7c5. ncr=nc (n-r)?
Why didn't we use in 6c1? Can anybody clear me please?
Why didn't we use in 6c1? Can anybody clear me please?
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