document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1206526>Question 1206526</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Below are the multiplication problems.\r<BR>\n" );
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document.write( "1). 17 x 23 ( I was informed to subtract 9 from 400).\r<BR>\n" );
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document.write( "2.  23 x 37 ( I was informed to subtract 49 from 900).\r<BR>\n" );
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document.write( "3). 18 x 30 ( I was informed to subtract 36 from 576).\r<BR>\n" );
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document.write( " What type of math strategy is this?    </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #844064 by </B><A HREF=/tutors/aboutme.mpl?userid=math_tutor2020><B>math_tutor2020(3817)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=math_tutor2020><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=844064\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> <font color=black size=3><BR>\n" );
document.write( "I'll focus on problem 1 only.\r<BR>\n" );
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document.write( "Note how 20 is the midpoint of 17 and 23.<BR>\n" );
document.write( "midpoint = (a+b)/2\r<BR>\n" );
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document.write( "17 x 23 = (20 - 3) x (20 + 3)<BR>\n" );
document.write( "17 x 23 = 20^2 - 3^2<BR>\n" );
document.write( "17 x 23 = 400 - 9<BR>\n" );
document.write( "17 x 23 = 391<BR>\n" );
document.write( "I used the difference of squares rule.<BR>\n" );
document.write( "The other two problems will use a similar approach.<BR>\n" );
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