Q&A #2647

Teachers' Lounge Discussion: Decimal manipulatives

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From: Pat Ballew

To: Teacher2Teacher Public Discussion
Date: 2000113015:45:23
Subject: A method using conversion to fractions

Sarah, There are many ways to multiply decimals, but here is one way that will help you understand what you are doing. 1) convert both decimals to a fractions (proper or improper) 2) Multiply the fractions in the usual way, multiply the numerators, multiply the denominators 3) Convert the answer back to decimals Example : Multiply .23 * .215 1) convert to 23/100 times 215/1000 2) multiply 23 * 215 for the numerator (4945) and 100*1,000=100,000 for the denominator... 3) now convert back to decimals, 4945/100,000 = .04945 Notice that it is almost like using whole numbers. Simon Stevin, the Dutch mathematician/Engineer who first made decimals popular in European mathematics, never thought of them as fractions at all. Good luck -Pat Ballew, for the T2T service Thanks for visiting our on-line community. Visit Teacher2Teacher again at http://mathforum.com/t2t/

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