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Free Powerpoint Templates

Random I nteresting Math Tricks (more importantly , how do they work ) HWW Math Club 11/28/2011. Free Powerpoint Templates. Does a number divide 2, 5, 10?. Devise a method to determine if some number , for instance 185924, is divisible by 2, 5, and 10 respectively .

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Free Powerpoint Templates

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  1. RandomInteresting Math Tricks (more importantly, how do theywork) HWW Math Club 11/28/2011 Free Powerpoint Templates

  2. Does a numberdivide 2, 5, 10? Devise a method to determine if somenumber, for instance 185924, is divisible by 2, 5, and 10 respectively. Just look at the last digit!

  3. Does a numberdivide 3, 9? Devise a method to determine if somenumber, for instance 185924, is divisible by 3 and 9 respectively. Add up the digits. It’s divisible if the sum of digits is divisible.

  4. Does a numberdivide 6, 15, 18, 45? Devise a method to determine if somenumber, for instance 185924, is divisible by thesenumbers. Combine the divisibility tests. If it’s divisible by 2 and by 3, it’s divisible by 6.

  5. Does a numberdivide 11? Devise a method to determine if somenumber, for instance 1362075, is divisible by 11. Sum up alternating digits: 5-7+0-2+6-3+1 = 0.

  6. Does a numberdivide 7 or 13? Devise a method to determine if somenumber, for instance 10663786, is divisible by 7 or 13. Sum up alternating triple digits: 786 – 663 + 10 = 133 whichis divisible by 7 but not 13.

  7. Last one isslightlydifferent If I have some money in the bankwith compound interest of a year (compoundedfrequently), how long doesittake for my money to double? Divideitfrom 72. If it’s 3%, ittakes about 72/3 = 24 years to double.

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