document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=104025>Question 104025</A>: <I><SPAN STYLE=\"word-break: break-all;\"> I am stuck on this word problem would you be able to help me work it out?  \r<BR>\n" );
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document.write( "A ball is thrown upward from the roof of a building 100 m tall with an initial velocity of 20 m/s.  When will the ball reach a height of 80 m?  \r<BR>\n" );
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document.write( "This problem has me confused I am not sure where to begin.  Thanks for your help.   </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #75699 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=75699\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> A ball is thrown upward from the roof of a building 100 m tall with an initial velocity of 20 m/s. When will the ball reach a height of 80 m?<BR>\n" );
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document.write( "This can be made into a quadratic equation with the three elements<BR>\n" );
document.write( "Let t = time in seconds<BR>\n" );
document.write( "1. Gravity (negative because it's accelerated downward) -4.9t^2<BR>\n" );
document.write( "2. Initial velocity (positive because it's thrown up-ward: + 20t<BR>\n" );
document.write( "3. Initial height above ground: +100<BR>\n" );
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document.write( " -4.9t^2 + 20t + 100 = height above ground<BR>\n" );
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document.write( "They want to know when will it be at a height of 80 ft:<BR>\n" );
document.write( "-4.9t^2 + 20t + 100 = 80<BR>\n" );
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document.write( "-4.9t^2 + 20t + 100 - 80 = 0; subtracted 80 from both sides<BR>\n" );
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document.write( "-4.9t^2 + 20t + 20 = 0<BR>\n" );
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document.write( "This is the quadratic formula: except we will be solving for t instead of x:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ ALIGN=MIDDLE  ALT=\"x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" > <BR>\n" );
document.write( "Substitute: a=-4.9; b=20; c=20<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-20+%2B-+sqrt%28+20%5E2+-+4+%2A+-4.9+%2A+20+%29%29%2F%282%2A-4.9%29+ ALIGN=MIDDLE  ALT=\"t+=+%28-20+%2B-+sqrt%28+20%5E2+-+4+%2A+-4.9+%2A+20+%29%29%2F%282%2A-4.9%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Do the math:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-20+%2B-+sqrt%28400+-+%28-392%29+%29%29%2F%28-9.8%29+ ALIGN=MIDDLE  ALT=\"t+=+%28-20+%2B-+sqrt%28400+-+%28-392%29+%29%29%2F%28-9.8%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-20+%2B-+sqrt%28400+%2B+392+%29%29%2F%28-9.8%29+ ALIGN=MIDDLE  ALT=\"t+=+%28-20+%2B-+sqrt%28400+%2B+392+%29%29%2F%28-9.8%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" >; minus a minus is a plus<BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-20+%2B-+sqrt%28792%29%29%2F%28-9.8%29+ ALIGN=MIDDLE  ALT=\"t+=+%28-20+%2B-+sqrt%28792%29%29%2F%28-9.8%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-20+%2B-+28.1425%29%2F%28-9.8%29+ ALIGN=MIDDLE  ALT=\"t+=+%28-20+%2B-+28.1425%29%2F%28-9.8%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "Solution 1<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-20+%2B28.1425%29%2F%28-9.8%29+ ALIGN=MIDDLE  ALT=\"t+=+%28-20+%2B28.1425%29%2F%28-9.8%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+8.1425%2F%28-9.8%29 ALIGN=MIDDLE  ALT=\"t+=+8.1425%2F%28-9.8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "t = -.83, this is NOT our solution<BR>\n" );
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document.write( "Solution 2:<BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+%28-20+-+28.1425%29%2F%28-9.8%29+ ALIGN=MIDDLE  ALT=\"t+=+%28-20+-+28.1425%29%2F%28-9.8%29+\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
document.write( "<IMG STYLE=\"max-width:80%;\" SRC=/cgi-bin/plot-formula.mpl?expression=t+=+-48.1425%2F%28-9.8%29 ALIGN=MIDDLE  ALT=\"t+=+-48.1425%2F%28-9.8%29\"   DISABLED_style= \"max-width:90%; height:auto;\" ><BR>\n" );
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document.write( "t = + 4.9 sec, this IS our solution<BR>\n" );
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