Teacher2Teacher |
Q&A #494 |
From: Loyd
To: Teacher2Teacher Public Discussion
Date: 2005030115:42:56
Subject: Re: Re: multiplication
Joan: That technique is neat. That is the first time I ever saw that. However, it is not to good when the numbers on the right are large (10-the number) but it still works but may get into negative numbers. The number on the lefe is the number of tens: For example: One that works: 9 1 7 3 (9-3 and 7-1=6) ------ 6 3 6 tens + 3=63 Try this one: 5 5 4 6 --------- -1 30 here you have to consider 4-5=-1 or actually -10. -10 + 30 = 20. I am not sure that a 3, 4 or 5th grade student can use this to great value. But it does work for some of the harder ones.
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