document.write( "Question 1008835: Tim drove halfway Indianapolis at 60 mi/h and the rest of the way at 80 mi/h. What was his average speed for the whole trip? \n" ); document.write( "

Algebra.Com's Answer #624414 by ikleyn(52776) $\"\"$ $\"About$

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document.write( "Let L be the distance Tim covered.\r\n" );
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document.write( "Since Tim drove half of the distance, , at the speed of 60 mph, he spent for it the amount of time / =  hours.\r\n" );
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document.write( "Since Tim drove the other half of the distance. , at the speed of 80 mph, he spent for it the amount of time / =  hours.\r\n" );
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document.write( "The average speed is the whole distance L divided by the time spent, which is  + , or \r\n" );
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document.write( " =  =  = 68.571 .\r\n" );
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document.write( "The value  is called the harmonic mean of values u and v.\r\n" );
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document.write( "Thus the average speed in this problem is the harmonic mean of the given speed 60 mph and 80 mph.\r\n" );
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document.write( "See also the lesson Calculating an average speed: a train going from A to B and back in this site.\r\n" );
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