There is a chance you will see an extra-easy (read “extra-quick”) problem in this category. Be alert for average problems that list an odd-numbered series of numbers that occur in sequence, like this one.
You can quickly see, since there are no numbers missing in the sequence and there is a “middle” number, that the answer to this one is 48.
Be careful, though—this does not work with even-numbered series like 14, 15, 16, 17, 18, and 19. This series has six items, so there is no “middle” number.