Answer to Question #149681 in Discrete Mathematics for Jellys

Question

A keyboard has its keys removed. If the last line of the letters were
jumbled, how many ways can I rearrange it so that consecutive letters
are beside each other?
A.120
B. 144
C. 156
D.196

Answer 1

The last line of the letters on a keyboard:

Z X C V B N M (7 letters)

Consecutive letters which are beside each other: N M

So, the jumbled letters: Z X C V B (5 letters)

Answer: A.

$N=5!=1\cdot2\cdot3\cdot4\cdot5=120$