Q. In how many ways can 21 English and 19 Hindi books be placed in a row so that no two Hindi books are together?
A) 1540
B) 1450
C) 1504
D) 1405
Explanation
(a)
First we fix the alternate position of English books. Then there are 22 vacant places for Hindi books.
Hence, total number of ways $= \ ^{22}C_{19} = \frac{22!}{3!9!} = 1540$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.