document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=585559>Question 585559</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Jay realizes he needs a mark of 100% on his next test in order to achive a 90%average for all his tests.However if he gets a mark of 70% on the next test,his average will be 87%.After he writes the next test,how many tests will he have written?<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #373447 by </B><A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><B>ankor@dixie-net.com(22740)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=ankor@dixie-net.com><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=ankor@dixie-net.com><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=373447\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Jay realizes he needs a mark of 100% on his next test in order to achieve a 90% average for all his tests.<BR>\n" );
document.write( "However if he gets a mark of 70% on the next test,his average will be 87%.<BR>\n" );
document.write( "After he writes the next test,how many tests will he have written?<BR>\n" );
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document.write( "Let n = total number of tests<BR>\n" );
document.write( "Let a = average of the test already taken<BR>\n" );
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document.write( "Get 100 on the last test equation<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28%28a%28n-1%29%2B100%29%29%2Fn ALIGN=MIDDLE  ALT=\"%28%28a%28n-1%29%2B100%29%29%2Fn\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 90<BR>\n" );
document.write( "a(n-1) + 100 = 90n<BR>\n" );
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document.write( "Get 70 on the last test equation<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=%28%28a%28n-1%29%2B70%29%29%2Fn ALIGN=MIDDLE  ALT=\"%28%28a%28n-1%29%2B70%29%29%2Fn\"   DISABLED_style= \"max-width:90%; height:auto;\" > = 87<BR>\n" );
document.write( "a(n-1) + 70 = 87n<BR>\n" );
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document.write( "Use elimination here<BR>\n" );
document.write( "a(n-1) + 100 = 90n<BR>\n" );
document.write( "a(n-1) +  70 = 87n<BR>\n" );
document.write( "--------------------subtraction eliminates a(n-1), find n<BR>\n" );
document.write( "0 + 30 = 3n<BR>\n" );
document.write( "n = 10 total tests taken<BR>\n" );
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document.write( "If you wish to prove this to yourself, solve for a in one of the equations, then check the average in the other equation<BR>\n" );
document.write( "9a + 100 = 90(10) </SPAN>\n" );
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