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Q&A #6524

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

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From: alex <chess3335@yahoo.com>
To: Teacher2Teacher Public Discussion
Date: 2006121318:57:50
Subject: Re:what is the expanded notation of 90? and write a number sentence

On 2002091701:59:58, Glenn Nienaber wrote:
>	
>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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