List of top Mathematics Questions on Permutations asked in JKCET

5 books in Math and 3 books in Physics are placed on a shelf so that the books on the same subject always remain together. The possible arrangements are
The number of permutations of 4 letters that can be made out of the letters of the word EXAMINATION is
$ \frac{1}{3!}+\frac{2}{5!}+\frac{3}{7!}+... $ is equal to