Over ninety challenging puzzles which will satisfy even the most demanding enthusiast. Some are more difficult than others but all can be solved with the nimble assistance of a simple four-function calculator. Most of these brain teasers involve only an elementary knowledge of higher mathematics; when more sophisticated information is required, parenthetical hints are included for those who may have forgotten the radius of the moon or the metric equivalent of one inch. A special note offers valuable information on using various kinds of calculators. And for those of you who like crossword puzzle but prefer numerals to words, there are several cross number puzzles.