Average Fuel Economy
Tom, driving his car, reset the "Average Fuel Economy" gauge and drove 3.0 km. on a level road with a reading of 7 AVG L/100 km. He then drove up a hill that had a uniform slope for 1.0 km. At the top of this hill the gauge read 12 AVG L/100 km.
Let "x" represent the average fuel usage rate while going up the hill.
On the second run on this same course he reset the "Average Fuel Economy" gauge sooner and drove "y" km. on this level road with a reading of 7 AVG L/100km. He then proceeded up the same hill, but this time the reading at the top of the hill was only 11 AVG L/100km.
State the sum x + y.
The answer is 31.
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1 solution
(x(1) + 7(3))/(3 + 1) = 12
(x + 21)/4 = 12
x + 21 = 48
x = 27
(27(1) + 7 ( y)) / (y + 1) = 11
27 + 7y = 11y + 11
16 = 4y
y = 4
x + y = 31