document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=971061>Question 971061</A>: <I><SPAN STYLE=\"word-break: break-all;\"> <BR>\n" );
document.write( "A plane flew 720 mi with a steady 30 mi/hr tailwind. The pilot then returned to the starting point, flying against the same wind. If the round-trip flight took 10 hr, what was the plane's airspeed?<BR>\n" );
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document.write( "A plane flew 720 mi with a steady 30 mi/hr tailwind. The pilot then returned to the starting point, flying against the same wind. If the round-trip flight took 10 hr, what was the plane's airspeed?<BR>\n" );
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document.write( "a = plane's airspeed<BR>\n" );
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document.write( "720/(a+30) + 720/(a-30) = 10<BR>\n" );
document.write( "72/(a+30) + 72/(a-30) = 1<BR>\n" );
document.write( "72(a-30) + 72(a+30) = a^2 - 900<BR>\n" );
document.write( "144a = a^2 - 900<BR>\n" );
document.write( "a^2 - 144a - 900 = 0<BR>\n" );
document.write( "(a - 150)*(a + 6) = 0<BR>\n" );
document.write( "a = 150 mi/hr<BR>\n" );
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