Question

Find the number of arrangements of letters in the word MUMBAI so that the letter B is always next to A.

Answer 1

There are 6 letters in the word MUMBAI.
These letters are to be arranged in such a way that B is always next to A.
Let us consider the AB as one unit. This unit with the other 4 letters in which M repeats twice, is to be arranged.
∴ Total number of arrangements when B is always next to A.
= `(5!)/(2!)`

= `(5 xx 4 xx 3 xx 2!)/(2!)`
= 60