How many words can be made from the letters of the word $DELHI$,if $L$ comes in the middle in every word?

The number of $4$-letter words,with or without meaning,each consisting of two vowels and two consonants that can be formed from the letters of the word $INCONSEQUENTIAL$,without repeating any letter,is:

The number of ways in which $n$ boys and $n$ girls can be arranged in a row such that all the boys are together and all the girls are also together is equal to

How many numbers can be formed using the digits $1, 2, 3, 4, 3, 2, 1$ such that odd digits always occupy odd positions?

In a class of $20$ students,in how many ways can the following prizes be awarded?
If the first and second prizes are for Mathematics,the first and second prizes for Physics,the first prize for Chemistry,and the first prize for English are to be awarded.

How many arrangements can be made using the letters of the word $CALCUTTA$?