to multiply by Trick 2 add the number to itself (example 2×9 = 9+9) 5 the last digit goes 5, 0, 5, 0, ... is always half of 10× (Example: 5x6 = half of 10x6 = half of 60 = 30) is half the number times 10 (Example: 5x6 = 10x3 = 30) 6 if you multiply 6 by an even number, they both end in the same digit. Example: 6×2=12, 6×4=24, 6×6=36, etc 9 the last digit goes 9,8,7,6, ... your hands can help! Example: to multiply 9 by 8, hold your 8th finger down, and count 7 and 2, the answer is 72 is 10× the number minus the number. Example: 9×6 = 10×6 - 6 = 60-6 = 54 if you add the answers digits together, you get 9. Example: 9×5=45 and 4+5=9. (But not with 9×11=99) 10 put a zero after it 11 up to 9x11: just repeat the digit (Example: 4x11 = 44) for 10x11 to 18x11: write the sum of the digits between the digits (Example: 15x11 = 1(1+5)5 = 165) Note: this works for any two-digit number, but if the sum of the digits is more than 9, you will have to carry the one (Example: 75x11 = 7(7+5)5 = 7(12)5 = 825). 12 is 10× plus 2×
Posted on: Sat, 01 Feb 2014 08:18:44 +0000
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