Mathemagic! Number Tricks
written by Lynda Colgan; illustrated by Jane Kurisu
2011 (Kids Can Press)
Source: Mebane Public Library
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If you teach elementary school or have children in the second grade or higher, you have probably learned the 9's multiplication trick. This is where you put both of your hands together with fingers (include thumbs!) spread and drop the number you are multiplying by 9. For example, if the problem is 9 x 7, you drop your seventh finger and you see that there are six fingers (tens) to the left and three fingers (ones) to the right. This gives you the answer of sixty-three. I've known about this trick for a couple of decades, but I was unaware of the 6 'n' up trick where you hold both hands with palms up to multiply numbers from 6 -9. Mathemagic! Number Tricks contains this trick and many more magical mathematical maneuvers. Not only do you learn how to do these tricks, but you also learn the math and history behind each trick. Other math secrets revealed include Napier's bones, Mummy Math, binary numbers, and card and dice tricks.
Students love math tricks. They enjoy playing with numbers and experimenting. This book would be a great resource for stretching student brains. Good math instruction teaches students to find more than one way to
solve a problem and to be able to explain how the solution was found. Mathemagic! will provide opportunities for students to play with traditional algorithms in a variety of ways. It will help you conjure up a cornucopia of math fun.