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Q&A #6524

Teachers' Lounge Discussion: Explaining the why's of multiplication place values

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From: Glenn Nienaber

To: Teacher2Teacher Public Discussion
Date: 2002091702:59:58
Subject: expanded notation

Perhaps showing them that when they multiply 287 x 394 they are not really multiplying 3 x 7 they are really mutliplying 300 x 7 287 = 200 + 80 + 7 394 = 300 + 90 + 4 300 x 200 = 2 x 3 =6 add 4 zeros = 60,000 300 x 80 = 3 x 8 = 24 add 3 zeros = 24,000 300 x 7 = 3 x 7 = 21 add 2 zeros 2,100 90 x 200 = 9 x 2 = 18 add 3 zeros = 18,000 90 x 80 = 7200 7,200 90 x 7 = 630 630 4 x 200 = 800 800 4 x 80 = 320 320 4 x 7 = 28 28 Now add the three partial products.

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