document.write( "Question 259134: Your average speed on the first half of a car trip is 70.0 km/h. How fast do you have to drive on the second half of the trip to achieve an average speed of 85.0 km/h for the whole trip? \n" ); document.write( "

Algebra.Com's Answer #190794 by Edwin McCravy(20054) $\"\"$ $\"About$

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Your average speed on the first half of a car trip is 70.0 km/h. How fast do you have to drive on the second half of the trip to achieve an average speed of 85.0 km/h for the whole trip?
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document.write( "Let's suppose the whole trip is 2D km, since time = distance/speed, you\r\n" );
document.write( "have to get there in  hours.  You have gone D km at 70 miles\r\n" );
document.write( "an hour so again since time = distance/speed you have used up \r\n" );
document.write( "hours of the  hours, and you have only  hours\r\n" );
document.write( "left to go the remaining D km.  Since speed = distance/time, the\r\n" );
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document.write( "speed =  \r\n" );
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document.write( "Can you simplify that compound fraction? If not post again asking how.\r\n" );
document.write( "The D's will cancel out, so the answer is independent of the distance D.\r\n" );
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document.write( "Answer km/h\r\n" );
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document.write( "Edwin

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