In the sequence 2 P E % 7 R A 4 # M 9 U T & 3 B I 6 K $ 5 N, which element lies exactly midway between the letter R and the letter B?

R stands at place 6 and B at place 16. The place exactly midway is (6 + 16) ÷ 2 = 11, and the eleventh element is 9. M at place 10 and U at place 12 flank the midpoint, so either follows from a count that is short or long by one; T at place 13 is the midpoint of the letters lying between R and B rather than of R and B themselves.