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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 <gniena@kyrene.org>
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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