Aptitude - Permutation and Combination - Discussion
Discussion Forum : Permutation and Combination - General Questions (Q.No. 14)
14.
In how many ways can 21 books on English and 19 books on Hindi be placed in a row on a shelf so that two books on Hindi may not be together?
Answer: Option
Explanation:
In order that two books on Hindi are never together, we must place all these books as under:
X E X E X E X .... X E X
where E - denotes the position of an English book and X that of a Hindi book.
Since there are 21 books on English, the number of places marked X are therefore, 22. Now, 19 places out of 22 can be chosen in
| 22C19 = 22C3 = | 22 x 21 x 20 | = 1540 ways. |
| 3 x 2 x 1 |
Hence, the required number of ways = 1540.
Discussion:
27 comments Page 3 of 3.
Teja said:
2 decades ago
hi, i can't understand with ur explanation...
Priti said:
2 decades ago
Hi.
What is means the 22c19 & 22c3 ?.
What is means the 22c19 & 22c3 ?.
Vishal said:
2 decades ago
Sambit. Great explanation.
Thanks.
Thanks.
Mahanthesh naik said:
9 years ago
Correct ans is= 22c19 * 21! *19!.
Mohan said:
2 decades ago
Gaurav is right
21P21 * 22P19
21P21 * 22P19
Ananth said:
2 decades ago
Hi Nikhil,
nCr = nC (n-r).
nCr = nC (n-r).
Pallavi said:
2 decades ago
quite tricky.........
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