document.write( "Question 875439: The question is: Rachel drove 600 miles to her destination. The return trip was made at a speed that was 10 mph slower. If the total travel time was 22 hours, how fast did Rachel travel on each part of the trip?\r
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document.write( "So far I know that I have to make a table chart where I make two equations. The First trip and another with the return trip. I know that the distance formula is d=r*t. My distance is 600 miles and one rate is r and the other one is r-10, since it was going 10 mph slower, but I have no idea on what to put for time because it gives me a total not each time for the two trips.\r
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document.write( "Please help:( \n" );
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Algebra.Com's Answer #528169 by jim_thompson5910(35256)![]() ![]() ![]() You can put this solution on YOUR website! Trip to destination:\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "d = r*t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600 = r*t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600/r = t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "t = 600/r\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "It takes 600/r hours to travel to the destination.\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "-------------------------------------------------------\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Return Trip:\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "d = r*t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "d = (r-10)*t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600 = (r-10)*t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600/(r-10) = t\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "t = 600/(r-10)\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "It takes 600/(r-10) hours to get back home.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "-------------------------------------------------------\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Add up the two times and set that equal to the total time 22\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Time1 + Time2 = Total Time\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600/r + 600/(r-10) = 22\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Now we solve for r\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600/r + 600/(r-10) = 22\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "r(r-10) = r(r-10)*22 ... multiply both sides by the LCD r(r-10) to clear out the fractions.\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "r(r-10) + r(r-10) = r(r-10)*22\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "(r-10)*600 + r*600 = r(r-10)*22 ... Notice how the fractions are gone after multiplying everything by the LCD\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600(r-10) + 600r = 22r(r-10)\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "600r-6000 + 600r = 22r^2 - 220r\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "1200r-6000 = 22r^2 - 220r\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "0 = 22r^2 - 220r - 1200r + 6000\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "0 = 22r^2 - 1420r + 6000\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "22r^2 - 1420r + 6000 = 0\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "2(11r-50)(r-60) = 0\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "11r-50 = 0 or r-60 = 0\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "11r = 50 or r = 60\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "r = 50/11 or r = 60\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "r = 4.54545 or r = 60\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "If r = 4.54545, then r-10 = 4.54545-10 = -5.45455\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "It makes no sense to have a negative speed. So we ignore the solution r = -5.45455\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "The only practical solution is r = 60\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "Because r = 60, r-10 = 60-10 = 50\r \n" ); document.write( " \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "So the speed on the way to the destination was 60 mph. The speed coming back was 50 mph. \n" ); document.write( " \n" ); document.write( " |