FLEX YOUR brain power like never before From acclaimed author Dr. Gary Gruber, whose proven critical-thinking methods have sold more than seven million books, this collection of mind-bending brain teasers is sure to challenge even the most experienced problem solver. Inside are logic puzzles, riddles, maddening math problems, mental games, and more "A ship is twice as old as the ship's boiler was when the ship was as old as the boiler is. The ratio...