Question 22
A sequence of 10 letters is made according to the following rules.
- The letter P can only be followed by Q or R.
- The letter Q can only be followed by R or S.
- The letter R can only be followed by S or T.
- The letter S can only be followed by T or P.
- The letter T can only be followed by P or Q.
How many possible sequences are there where the first, fourth, and tenth letters are all Q?
- The letter P can only be followed by Q or R.
- The letter Q can only be followed by R or S.
- The letter R can only be followed by S or T.
- The letter S can only be followed by T or P.
- The letter T can only be followed by P or Q.
How many possible sequences are there where the first, fourth, and tenth letters are all Q?