document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=382389>Question 382389</A>: <I><SPAN STYLE=\"word-break: break-all;\"> If a rocket is fired vertically into the air with a speed of 368 feet per second, its height at time t seconds is given by h(t)=-16tsquared+368t.  How long will the rocket be in the air?  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #271007 by </B><A HREF=/tutors/aboutme.mpl?userid=nerdybill><B>nerdybill(7384)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=nerdybill><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=nerdybill><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=271007\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Given:<BR>\n" );
document.write( "h(t)=-16t^2+368t<BR>\n" );
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document.write( "You can set h(t) to zero and solve for t:<BR>\n" );
document.write( "h(t)=-16t^2+368t<BR>\n" );
document.write( "0=-16t^2+368t<BR>\n" );
document.write( "0=16t^2-368t<BR>\n" );
document.write( "0=16t(t-23)<BR>\n" );
document.write( "t = {0, 23}<BR>\n" );
document.write( "answer: 23 seconds<BR>\n" );
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document.write( "OR, you can think of like:<BR>\n" );
document.write( "The vertex is at it's highest point AND at mid-flight.  If we found time (t) when it reaches the vertex, we simply double it for the answer.<BR>\n" );
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document.write( "time (t) at vertex:<BR>\n" );
document.write( "t = -b/(2a) = -368/(2*(-16)) = -368/(-32) = 11.5 sec<BR>\n" );
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document.write( "Answer:<BR>\n" );
document.write( "2*11.5 = 23 seconds<BR>\n" );
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document.write( " </SPAN>\n" );
document.write( "</TD></TR></TABLE>\n" );