document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=878045>Question 878045</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Hi, I need help with this word problem if someone could help me i would greatly appreciate it. \r<BR>\n" );
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document.write( "A fireworks shell is shot straight up with an initial velocity of 120 feet per second. Its height s in feet after t seconds is approximated by the equations s=120t-16t^2. if the shell is designed to explode when it reaches its maximum height, how long after being fired, and at what height, will the fireworks appear in the sky? \r<BR>\n" );
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document.write( "thank you for your time.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #529691 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=529691\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> s = 120t-16t^2<BR>\n" );
document.write( "this is an equation for a parabola that opens downward<BR>\n" );
document.write( "the time t where it changes direction is -b/2a, therefore<BR>\n" );
document.write( "t = -(120) / 2(-16) = 120/32 = 3.75 seconds<BR>\n" );
document.write( "the height s is<BR>\n" );
document.write( "s = 120(3.75) - 16(3.75)^2 = 435.9375 feet<BR>\n" );
document.write( "therefore in 3.75 seconds the fireworks will explode at at height of 436 feet\r<BR>\n" );
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