IQ puzzles

These 500 puzzles offer the ultimate challenge for solvers who want to pit their wits against crafty conundrums, stretch their mental powers, and sharpen their IQs. The degree of difficulty keeps rising in each of the 20 sections, so work through them in methodical order to find mathematical patterns that seem to reoccur and visual clues that overlap. That helps as the problems get harder, but beware: just when you think you're caught on to the trick, it changes