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 11 of 14.
Akshay said:
1 decade ago
@Venki.
If the order doesn't matter, it is a Combination.
If the order does matter it is a Permutation.
If the order doesn't matter, it is a Combination.
If the order does matter it is a Permutation.
Venki said:
1 decade ago
Guys do you have any idea when to use permutations or combinations?
Pankaj said:
1 decade ago
Would you please explain in question they ask only for the three man combination then why you have taken 4m and 1m and all five men possibilities?
Shiva said:
1 decade ago
@Olga.
You have removed only the condition where you have only two men, but you have to remove the condition where one men and no men are present. i.e. 7c2*6c3 + 7c1*6c4 +7c0*6c5 has to be removed from 13c5.
You have removed only the condition where you have only two men, but you have to remove the condition where one men and no men are present. i.e. 7c2*6c3 + 7c1*6c4 +7c0*6c5 has to be removed from 13c5.
Sri Ram said:
1 decade ago
Is there any shortcut for doing the steps like 13c5 like that. These steps are taking too much time?
Olga said:
1 decade ago
I tried to calculate it differently. First, I calculated number of combinations with less than 3 men in them: 7C2*6C3=21*20=420. Then, total number of combinations possible: 13C5=1287. After that I deducted number of combinations with less than 3 men in them from total number of combinations: 1287-420= 862. However the answer is incorrect. Please, where is my mistake?
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.
Vibhor said:
1 decade ago
How to know when to use permutation and when to use combination ?
Dipak said:
1 decade ago
@divya because there is a condition that, 3 man's are compulsory has to be select..
Divya said:
1 decade ago
May be 5 womans is also possible, why we don't take that option?
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