document.write( "Question 216188: A car travels from A to B. First half of the distance it moves with a speed 60 mph, and the second half - with a speed 40 mph. Find the average speed of a car for the whole trip. \n" ); document.write( "
Algebra.Com's Answer #163266 by nerdybill(7384)\"\" \"About 
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A car travels from A to B. First half of the distance it moves with a speed 60 mph, and the second half - with a speed 40 mph. Find the average speed of a car for the whole trip.
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\n" ); document.write( "Applying the \"distance formula\" (d=rt):
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\n" ); document.write( "Let x = total distance from A to B
\n" ); document.write( "then
\n" ); document.write( "\"time traveled 1st half\" = (x/2)/60 = x/120
\n" ); document.write( "\"time traveled 2nd half\" = (x/2)/40 = x/80
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\n" ); document.write( "Total time: x/120 + x/80
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\n" ); document.write( "Average speed is
\n" ); document.write( "\"total distance\"/\"total time\"
\n" ); document.write( "= x/(x/120 + x/80)
\n" ); document.write( "Dividing numerator and denominator by 'x':
\n" ); document.write( "= 1/(1/120 + 1/80)
\n" ); document.write( "= 10/(1/12 + 1/8)
\n" ); document.write( "= 10/(2/24 + 3/24)
\n" ); document.write( "= 10/(5/24)
\n" ); document.write( "= 240/5
\n" ); document.write( "= 48 mph
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