document.write( "Question 1174166: A biology teacher drives from Naperville over the Cleveland to visit her sister. During the trip there, she travels the first half of the time at 65 km/hr and the second half the time at 95 km/hr. When she comes back, she drives the first half the distance at 65 km/hr and the second half of the distance at 95 km/hr. What is her average speed coming back from Cleveland?\r
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document.write( "I am confused how to calculate this. I thought it might just be the average of the two speeds but that is not the correct answer. Also, I tried to set up an equation, but solving this did not give me the right answer. The equation I thought might work (wrong answer of 78.6 km) was D/160 + D(1/260 + 1/380), and then divided 1 by 0.0127 (sum of all the D terms). Any help would be greatly appreciated. Thank you.\r
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Algebra.Com's Answer #799569 by ikleyn(52803)![]() ![]() You can put this solution on YOUR website! . \n" ); document.write( "A biology teacher drives from Naperville over the Cleveland to visit her sister. \n" ); document.write( "During the trip there, she travels the first half of the time at 65 km/hr and the second half the time at 95 km/hr. \n" ); document.write( "When she comes back, she drives the first half the distance at 65 km/hr and the second half of the distance at 95 km/hr. \n" ); document.write( "What is her average speed coming back from Cleveland? \n" ); document.write( "~~~~~~~~~~~~~\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Solution\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \r\n" ); document.write( "Let \" t \" be her total time driving from N to C.\r\n" ); document.write( "\r\n" ); document.write( "\r\n" ); document.write( "Then the total distance from N to C is d = 0.5t*65 + 0.5t*95 = 0.5t*(65+95) = 0.5t*160 = 80t kilometers.\r\n" ); document.write( "\r\n" ); document.write( "\r\n" ); document.write( "Half the distance is 40t kilometers.\r\n" ); document.write( "\r\n" ); document.write( "\r\n" ); document.write( "When driving back (from C to N), the total driving time is T =\r \n" ); document.write( "\n" ); document.write( "Solved.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "------------\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Is everything clear to you in my solution ?\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "When you complete read it, do not forget to post your \"THANKS\" to me for my teaching.\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "///////////////\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "For the problem, it does not matter, who is the driver: \"biology teacher\", or carpenter, or sales manager, or astronaut, \n" ); document.write( "or vice-president, or anybody else.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Therefore, naming his (or her) specialty is IRRELEVANT to the problem.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "I know that 80% of problems in US Math textbooks are formulated this way.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "It is NOT an argument that they all are correct; they all are WRONG.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "They teach young students to think incorrectly, and, in addition, they treat the students inadequately . . . \r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "As a result, when such a student sees the words \"vice-president\" instead of \"biology teacher\", \n" ); document.write( "he (or she) thinks that it is another problem . . . \r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |