Q. There are $n$ different books and $m$ copies of each in a college library. The number of ways in which a student can make a selection of one or more books is
A) $(m + 1)^{n}$
B) $\frac{(mn)!}{(m!)^{n}}$
C) $\ ^{mn}C_{n} \times \ ^{n}C_{1}$
D) $(m + 1)^{n} - 1$
Explanation
(d)
There are $(m + 1)$ choices for each of $n$ different books. So, the total number of choice is $(m + 1)^{n}$ including one choice in which we do not select any book.
Hence, the required number of ways is $(m + 1)^{n} - 1$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.