document.write( "Question 427559: Please help me set up this problem:\r
\n" ); document.write( "\n" ); document.write( "\"When Ace Airlines changed to planes that flew 100km/hour faster than its old ones, the time of its 2800 km Dallas-Seattle flight was reduced by 30 minutes. Find the speed of the new planes.\" \n" ); document.write( "

Algebra.Com's Answer #297357 by mananth(16946) $\"\"$ $\"About$

You can put this solution on YOUR website!
original speed = x
\n" ); document.write( "increased speed = x+100\r
\n" ); document.write( "\n" ); document.write( "...
\n" ); document.write( "Original time = 2800/x\r
\n" ); document.write( "\n" ); document.write( "Time after speed increase = 2800/(x+100)\r
\n" ); document.write( "\n" ); document.write( "2800/x - 2800/(x+100)=1/2\r
\n" ); document.write( "\n" ); document.write( "LCD = x(x+100)
\n" ); document.write( "multiply by x(x+100)
\n" ); document.write( "2800(x+100)-2800*x= 1/2* x(x+100)
\n" ); document.write( "2800x+280000-2800x=1/2(x^2+100x)
\n" ); document.write( "5600x+560000-5600x= x^2+100x
\n" ); document.write( "x^2+100x-560000=0
\n" ); document.write( "Find the roots of the equation by quadratic formula
\n" ); document.write( "
\n" ); document.write( "a= 1 ,b= 100 ,c= -560000
\n" ); document.write( "
\n" ); document.write( "b^2-4ac= 10000 + 2240000
\n" ); document.write( "b^2-4ac= 2250000
\n" ); document.write( " $\"x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29\"$
\n" ); document.write( " $\"x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29\"$
\n" ); document.write( " $\"x1=%28-2%2Bsqrt%28664%29%29%2F%282%29\"$
\n" ); document.write( "x1=( -100 + 1500 )/ 2
\n" ); document.write( "x1= 700
\n" ); document.write( "x2=( -100 -1500 ) / 2
\n" ); document.write( "x2= -800
\n" ); document.write( "Ignore negative value
\n" ); document.write( "plane speed = 700 mph
\n" ); document.write( "New plane speed = 800 mph\r
\n" ); document.write( "\n" ); document.write( " \n" ); document.write( "

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