There are 10 copies each of 4 different books. In how many ways can they be arranged on a shelf? Answers
A) 40!	B) 40!/10!	C) 40!/4!	D) 40!/10	E) 40!/{10!^4}
The total number of ways in which a total N items, out of which p are identical of one type, q are identical of another type and rest are different, can be arranged in a line is N!/{p!q!}   Here we have a total of 40 books, among which 10 books of one type are identical, 10 books of another type are identical, 10 books of another type are identical, and the remaining 10 books are also identical.   Hence the number of arrangements shall be 40!/{10!10!10!10!}=40!/{10!^4}   Ans 40!/{10!^4}
<result>E</result>
There are 10 copies each of 4 different books. In how many ways can they be arranged on a shelf?