document.write( "Question 543154: With a north wind blowing at 20 mi/hr a helicopter flies due north for 30 miles and then returns. If the total traveling time was 48 mins find the helicopters speed in still air. \n" ); document.write( "
Algebra.Com's Answer #354773 by mananth(16946)\"\" \"About 
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Helicopter speed x mph
\n" ); document.write( "wind speed 20 mph
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\n" ); document.write( "against wind x- 20 mph
\n" ); document.write( "with wind x+ 20 mph
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\n" ); document.write( "Distance= 30 miles
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\n" ); document.write( "Time against + time with = 0.8 hours
\n" ); document.write( "t=d/r \r
\n" ); document.write( "\n" ); document.write( "30 /( x + 20 ) + 30 /(x - 20 ) = 0.8
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\n" ); document.write( "LCD = (x - 20 ) ( x + 20 )
\n" ); document.write( "30 *( x - 20 ) + 30 (x + 20 ) = 0.8
\n" ); document.write( "30 x - 600 + 30 x + 600 = 0.8 ( x ^2 - 400 )
\n" ); document.write( "60 x = 0.8 x ^2 - 320
\n" ); document.write( "0.8 x ^2 - -60 x - 320
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\n" ); document.write( "Find the roots of the equation by quadratic formula
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\n" ); document.write( "a= 0.8 , b= -60 , c= -320
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\n" ); document.write( "b^2-4ac= 3600 + 1024
\n" ); document.write( "b^2-4ac= 4624 \"%09sqrt%28%094624%09%29=%0968%09\"
\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=( 60 + 68 )/ 1.6
\n" ); document.write( "x1= 80
\n" ); document.write( "x2=( 60 -68 ) / 1.6
\n" ); document.write( "x2= -5
\n" ); document.write( "Ignore negative value = 80 mph speed \r
\n" ); document.write( "\n" ); document.write( "m.ananth@hotmail.ca
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