document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1029343>Question 1029343</A>: <I><SPAN STYLE=\"word-break: break-all;\"> How many 3-digit numbers are multiple of 21?<BR>\n" );
document.write( "I can solve it by counting there is another way to solve this type of problem <BR>\n" );
document.write( "Thanks </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #644370 by </B><A HREF=/tutors/aboutme.mpl?userid=robertb><B>robertb(5830)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=robertb><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/cgi-bin/show-face.mpl?user=robertb><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=644370\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> The highest three-digit number divisible by 21 is 987, while the smallest is 105.<BR>\n" );
document.write( "Use the formula for the nth term of an AP \r<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%5Bn%5D+=+a%5B1%5D+%2B+%28n-1%29d ALIGN=MIDDLE  ALT=\"a%5Bn%5D+=+a%5B1%5D+%2B+%28n-1%29d\"   DISABLED_style= \"max-width:90%; height:auto;\" >, where <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%5Bn%5D+=+987 ALIGN=MIDDLE  ALT=\"a%5Bn%5D+=+987\"   DISABLED_style= \"max-width:90%; height:auto;\" > and <IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=a%5B1%5D+=+105 ALIGN=MIDDLE  ALT=\"a%5B1%5D+=+105\"   DISABLED_style= \"max-width:90%; height:auto;\" >, and d = 21.\r<BR>\n" );
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document.write( "==> 987 = 105 + (n-1)21 ==> 882 = 21(n-1)  ==> 42 = n-1 ==> n = 43.\r<BR>\n" );
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document.write( "Thus there are 43 such numbers.\r<BR>\n" );
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document.write( "Note: I know there is another, much shorter (or more elegant) method in doing this, and expect another tutor to post it. </SPAN>\n" );
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