document.write( "Question 1084467: Mentally compute the product of 49 and 19. Describe the steps that you mentally went through to get your answer. Prove your answer using standard multiplication. Show your work. \n" ); document.write( "

Algebra.Com's Answer #698557 by ikleyn(52835) $\"\"$ $\"About$

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document.write( "Based on an identity (x-1)*(y-1) = xy - (x+y) + 1, substitute x= 50, y= 20 and do this:\r\n" );
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document.write( "1.  Calculate 50*20 = 1000 (mentally).\r\n" );
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document.write( "2.  Calculate 50 + 20 = 70 (mentally).\r\n" );
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document.write( "3.  Subtract 70 from 1000 to get 930 (mentally).\r\n" );
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document.write( "4.  Finally, add 1 to 930 to get 931 (mentally).\r\n" );
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