Square a 2 Digit Number, for this example 37: *.Look for the nearest 10 boundary *.In this case up 3 from 37 to 40. *.Since you went UP 3 to 40 go DOWN 3 from 37 to 34. *.Now mentally multiply 34x40 *.The way I do it is 34x10=340; *.Double it mentally to 680 *.Double it again mentally to 1360 *.This 1360 is the FIRST interim answer. *.37 is "3" away from the 10 boundary 40. *.Square this "3" distance from 10 boundary. *.3x3=9 which is the SECOND interim answer. *.Add the two interim answers to get the final answer. *.Answer: 1360 9 = 1369 With practice this can easily be done in your head.
Posted on: Tue, 20 Aug 2013 16:33:55 +0000
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