No complicated set-up for this one! Quite simply, what number comes next and why?
2 4 6 9 11 15 20 ??

Each term of the sequence use precisely two letters when written in Roman numerals.
Thus, the roman numeral representation of the missing term must be XL which follows XX (20).
Thus, the required missing term is 40.

Nice Problem.

Posted by K Sengupta on 2007-03-09 04:40:37