Question

The number of 7-letter sequences which use only P, Q, R (and not necessarily all of these) and with P never immediately followed by Q, Q never immediately followed by R and R never immediately followed by P is

• A. 384
• B. 192
• C. 288
• D. none of these

Answer 1

The correct option is B

192

We have 3 choices for the first letter, and 2 for each subsequent letter. So 3$\times$2${}^6$ = 192