http://nysmithmath.forumotion.net/fast-math-tricks-f14/-t1.htm Quick and easy math tricks to use in problem solving Sat, 27 Dec 2008 00:37:56 GMT 10 http://intranet.meriden.k12.ct.us/maloney/maloney_WEB/clubs/images/MathSymbols50_000.jpg http://nysmithmath.forumotion.net/fast-math-tricks-f14/-t1.htm http://nysmithmath.forumotion.net/fast-math-tricks-f14/quickly-multiply-numbers-close-to-multiples-of-10-t44.htm Archis The following is a five minute video providing a smarter way of multiplying numbers close to multiples of 10. Testing the new method versus the speed of a TI-83 calculator, you'll find it much faster. THE BASIC PRINCIPLE: (10+X)(10+Y)= 100+ 10X+ 10Y+XY= 10(10+X+Y)+XY In other word, add the units digit of the second number (Y) to the first number (10+X). This will serve as your hundreds and tens digit (that's why it is multiplied by 10 above.) Add the product of the units digit (XY) ... Fast Math Tricks Fri, 26 Dec 2008 02:05:41 GMT http://nysmithmath.forumotion.net/fast-math-tricks-f14/quickly-multiply-numbers-close-to-multiples-of-10-t44.htm#284 http://nysmithmath.forumotion.net/fast-math-tricks-f14/quickly-multiply-numbers-close-to-multiples-of-10-t44.htm http://nysmithmath.forumotion.net/fast-math-tricks-f14/how-to-easily-square-numbers-ending-in-5-t45.htm Archis The following is an easy method to square numbers with a units digit of 5. Begin with the multiplication of 65*65 or something similar Next add one to the tens digit of the number being squared: 6+1=7 Multiply the result with the original number: 6*7= 42 Place this number before 25 to get 4225 This process should work each time The algebra behind this is as follows: 10X+5 should be represent any number with a units digit of 5. (10X+5)(10X+5) 100X^2 + 100X + 25 (10X ... Fast Math Tricks Sat, 27 Dec 2008 00:37:56 GMT http://nysmithmath.forumotion.net/fast-math-tricks-f14/how-to-easily-square-numbers-ending-in-5-t45.htm#285 http://nysmithmath.forumotion.net/fast-math-tricks-f14/how-to-easily-square-numbers-ending-in-5-t45.htm