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 4 of 14.
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.
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?
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?
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.
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?
Venki said:
1 decade ago
Guys do you have any idea when to use permutations or combinations?
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.
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.
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.
Riya said:
1 decade ago
There are 4 types of permutation & its solved by diff formula. Which type is this?
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