IndiaBIX

Aptitude - Permutation and Combination - Discussion

Discussion Forum : Permutation and Combination - General Questions (Q.No. 1)
Permutation and Combination
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?
564
645
735
756
None of these
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)
= 7 x 6 x 5 x 6 x 5 + (7C3 x 6C1) + (7C2)
3 x 2 x 1 2 x 1
= 525 + 7 x 6 x 5 x 6 + 7 x 6
3 x 2 x 1 2 x 1
= (525 + 210 + 21)
= 756.

Discussion:
137 comments Page 8 of 14.
Ajay said:   10 years ago
7C5 written as 7C2 because 7C5 = 7C(7-5) both having same values from formula nCr = nC(nr).
Shaifali said:   4 years ago
Well explained @Nagu.

But I don't understand why do we need to multiply? why can't we add?
Ankit said:   1 decade ago
Friends, please tell me how to identify whether question is of permutation or combination?
Aishwarya said:   7 years ago
@Dadasaheb.

The total ways-5!=120.
if siblings sit together-2!4!=48.
Hence; 120-48=72.
(2)
Bhargav said:   1 decade ago
How can you take a 3 men 2 women 4men and 1women and a 5 men please solve easy method.
Riya said:   1 decade ago
There are 4 types of permutation & its solved by diff formula. Which type is this?
Sharon said:   1 decade ago
GUYS.

How do we analyse that whether permutation or combination has to be used here?
Bhawani said:   1 decade ago
I have a small doubt. Why we didn't divide it like this 7c3*6c2+7c4*6c1+7c5*6c0/13c5?
Dipak said:   1 decade ago
@divya because there is a condition that, 3 man's are compulsory has to be select..
Shiva said:   1 decade ago
How do you find weather give problem can solved by combinations or permutation?
Post your comments here:

Your comments will be displayed after verification.

Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers