Aptitude - Permutation and Combination - Discussion
Discussion Forum : Permutation and Combination - General Questions (Q.No. 11)
11.
In how many ways can a group of 5 men and 2 women be made out of a total of 7 men and 3 women?
Answer: Option
Explanation:
| Required number of ways = (7C5 x 3C2) = (7C2 x 3C1) = |  |
7 x 6 | x 3 |  |
= 63. |
| 2 x 1 |
Discussion:
51 comments Page 1 of 6.
Priya said:
2 decades ago
How? I can't understand this problem.
Sahithya said:
1 decade ago
Hi priya,.
We have to select 5men out of 7 men, this can be done in 7C5 ways
= 7C2 [Ref: nCr=nC (n-r) ].
And also we hav to select 2women out of 3 women, this can be done in 3C2 ways = 3C1.
As these two combinations are compulsry, we hav to multiply 7C2 and 3C1.
I think you understand.
We have to select 5men out of 7 men, this can be done in 7C5 ways
= 7C2 [Ref: nCr=nC (n-r) ].
And also we hav to select 2women out of 3 women, this can be done in 3C2 ways = 3C1.
As these two combinations are compulsry, we hav to multiply 7C2 and 3C1.
I think you understand.
Binushree said:
1 decade ago
How to multiply?
Karthik said:
1 decade ago
Why can't we multiply 7C5 nd 3C2 directly ?
Suvarna said:
1 decade ago
It takes more time to calculate 7c5 than 7c2& 3C2 than 3C1, to improve the speed we are doing like this.
Jat said:
1 decade ago
(7C5 x 3C2) = (7C2 x 3C1)
This step i can't understand.
Please explain me.
This step i can't understand.
Please explain me.
Manasa said:
1 decade ago
@jat
its just formula
n =n
c c
r n-r
n=7,r=5
7C5=7C2
its just formula
n =n
c c
r n-r
n=7,r=5
7C5=7C2
Zalak said:
1 decade ago
(7C5 x 3C2) = (7C2 x 3C1)
This step I can't understand. Please explain me.
This step I can't understand. Please explain me.
Kavu said:
1 decade ago
(7C2 x 3C1) = (7/2 x 6/1) x 3= 63.
How it comes?
How it comes?
ACHUTHARAJ said:
1 decade ago
Basic formula nCr = nCn-r
so 7C7-5 = 7C2
3C3-2 = 3C1
so 7C7-5 = 7C2
3C3-2 = 3C1
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