Teacher2Teacher |
Q&A #113 |
From: Cindy Wilkins
(for Teacher2Teacher Service)
Date: May 25, 1998 at 19:07:26
Subject: 7-8th grade multiplication and division
I agree with Suzanne - music is an excellent way to learn multiplication facts. With my remedial 8th grade students, I used the repeated addition and subtraction method. (I'm not sure about the authenticity of this next story, but it really grabs my kids attention: repeated addition and subtraction is how it was taught up until WWI - students who had figured out the 'short cut', i.e. multiplication tables, were pegged as officers while the rest became infantry. It wasn't long before the multiplication tables became an integral part of education.) Here's how it works: Division: just keep subtracting - when your remainder is too small for another subtraction, count how many times you performed the subtraction operation and record: bring down the next number and repeat. _____ 23/425 23 -- 19 I can't subtract again, so I put a 1 in the 10's place 5 bring down the 5 (not a separate line, please) --- 195 23 --- 172 23 --- 149 23 --- 126 23 --- 103 23 --- 80 23 --- 57 23 --- 34 23 --- 11 I can't go any farther. I subtracted 8 more times and only have 11 of the 23 I need to subtract again, so my answer is 18 11/23. My students practiced multiplying and dividing throughout the year, and by the end of the year, only one student still required this technique - the others had learned enough of their tables to make the process much quicker and much less paper-intensive. Example: Multiply 23 x 42 --- 23 23 first, write 23 down twice, then mark off the units column 23x 23x 23x 23x now, write 23 four times with the units column marked off ---- 966 add your columns - Cindy
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