Question

Write the number of arrangements of the letters of the word BANANA in which two N's come together.

Answer 1

There are 6 letters in hte word 'BANANA' out of which 3 are A's 2 are N's and the rest are all distinct.

Considering both N's together and treating them as one letter we have 5 letters.

These 5 letters can be arranged in $\frac{5!}{3!}$

= $\frac{5\times 4\times 3!}{3!}$

= 20

Hence, the 5 letters can be arranged in 20 ways.