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.
Deus Simon said:
1 decade ago
The questions influencable but you did not talk about the of an event to occur.
Akash said:
1 decade ago
Can anyone please explain what does C imply here?
VATSAL KHANDELWAL said:
1 decade ago
Dear @Akash,
You mustn't try these if you don't even know the meaning of "c".
Else what I can say is that.
"c" simply means "combination".
But you can't understand if you haven't read the chapter.
You mustn't try these if you don't even know the meaning of "c".
Else what I can say is that.
"c" simply means "combination".
But you can't understand if you haven't read the chapter.
Ashok said:
1 decade ago
Please give a correct explanation to combination and permutation?
D.Yogapriya said:
1 decade ago
Is there any other simple way to solve this 1st problem?
Pandu said:
1 decade ago
@Priyanka das.
7C2 has taken since in the last case we need to take 5 men so that you may be understood, its actually 7c5 when in nCr if n value is more than half of n value we need to use formula as nC(n-r)so implies n=7, r=5 since r is more than half of n we used as 7C(7-5) it becomes 7C2. OK I HOPE you got it.
7C2 has taken since in the last case we need to take 5 men so that you may be understood, its actually 7c5 when in nCr if n value is more than half of n value we need to use formula as nC(n-r)so implies n=7, r=5 since r is more than half of n we used as 7C(7-5) it becomes 7C2. OK I HOPE you got it.
Ankit said:
1 decade ago
Friends, please tell me how to identify whether question is of permutation or combination?
Gokul said:
1 decade ago
It is simple to identify the given problem is permutation or combination. It is just by common sense ya. In permutation, there is arrangement of things. But in combination it is selection. I hope you understand.
Ales said:
1 decade ago
Please can you tell me why we use combination instead of permutation?
Pavz said:
1 decade ago
You can't use 7C3*10C2.
Because suppose the 5 men are ABCDE and 2 women are XY.
If you say 7C3*10C2 let the men be ABC and the other two be DX
then the committee will be ABCDX.
If you consider another way for 7C3*10C2 let da men be ABD and the other two be CX.
Now the committee is ABDCX.
But ABCDX = ABDCX.
But by using 7C3*10C5 it is taken as two separate ways.. but it is one. So that method is wrong :).
Because suppose the 5 men are ABCDE and 2 women are XY.
If you say 7C3*10C2 let the men be ABC and the other two be DX
then the committee will be ABCDX.
If you consider another way for 7C3*10C2 let da men be ABD and the other two be CX.
Now the committee is ABDCX.
But ABCDX = ABDCX.
But by using 7C3*10C5 it is taken as two separate ways.. but it is one. So that method is wrong :).
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