Question

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

Answer 1

As, 

It is required that two N’s come together, 

So, 

Let us consider {NN} as a single object. 

Thus we have, 

5 objects {B}, {A}, {NN}, {A}, {A}, and there are 3 A's. 

So, 

The number of arrangements in which the two N's are together is 

= \(\frac{5!}{3!}\)

= 20