Algebra.Com's Answer #830945 by ikleyn(52875)![\"\"](\"/images/stars/stars-13.gif\")  
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document.write( "Joseph traveled from Boston to Framingham at 50 mph and then back to Boston at 40 mph.
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document.write( "What was Joseph's average speed on the round trip?
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document.write( "When the average velocities  and  are given for each of the two parts of a round trip,\r\n" );
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document.write( "there is a standard formula to calculate the average speed  of the total trip.\r\n" );
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document.write( "This formula is V =  , and it gives the answer momentarily V =  =  = 44  mph = 44.444 mph (rounded). \r\n" );
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document.write( "When you get such problem, it is expected that you know this formula and use it,\r\n" );
document.write( "as well as it is expected that you know how to derive this formula.\r\n" );
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document.write( "Deriving is very simple. \r\n" );
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document.write( "If one way distance is D, then the time traveling with speed is  ,\r\n" );
document.write( "while the time traveling with speed is  .\r\n" );
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document.write( "So, the total time of the two-ways round trip is + .\r\n" );
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document.write( "To find the average speed of the round trip, you divide total distance 2D by the total time + .\r\n" );
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document.write( "You get then\r\n" );
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document.write( " V =  = cancel common factor D in the numerator and in the denominator =  = simplify the fraction = ,\r\n" );
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document.write( "as it was announced above.\r\n" );
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document.write( "You need to learn this formula and memorize it, and then you will be able to solve \r\n" );
document.write( "hundreds similar problems mechanically, without any mental efforts.\r\n" );
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document.write( "When you get this level, it will mean that you know the method.\r\n" );
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document.write( "In addition, you will be able to teach other people (including your children and grand-children) on how to solve such problems \r\n" );
document.write( "quickly, properly and in a right way.\r\n" );
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document.write( "Solved, with full explanations.\r
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document.write( "To see other similar solved problems, look into these lessons\r
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document.write( " - Calculating an average speed: a train going from A to B and back \r
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document.write( " - One more problem on calculating an average speed \r
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document.write( "in this site.\r
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