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All it takes to solve these problems are addition, subtraction, multiplication, and division. Sound simple?Well...not quite. But fun? Absolutely, because you find the answers by thinking of each puzzle as a game, where you have the exciting challenge of testing, probing, and overcoming an opponent's weaknesses. What must you do to "win"? There are geometry puzzles involving figures to cut in equal parts: use your visual intuition and mental flexibility to manipulate the pieces. Then, play "pentominoes," or five-sided dominoes: it's one of the world's most popular types of jigsaw and a delightfully tricky challenge. Still more involve moves across a board and drawings. Give this one a shot: Even upside down, a bat can continue to use its digital watch, because some hours are the same even when viewed in reverse. For example, this is what happens with 12:21. We call these hours reversible. What is the shortest interval between two reversible hours? Victory will be sweet when you vanquish these puzzles! Answer: The shortest interval between two reversible hours is between 9:56 and 10:01, and is five minutes. 5 3/8 X 8 1/4. 35 B&W Illustrations Distributed by Syndetic Solutions, Inc.