Question 954043: After a rise in the price of petrol, the
driven mileage dropped down by 6.7%. However the fuel
cost increased by 4.5%. By what percentage did the
petrol price rise?
Answer by Theo(13342)   (Show Source):
You can put this solution on YOUR website! if i understand the question correctly, i believe the increase in the cost of fuel per mile is 12%.
here's why:
at the current prices, people drove a total of y miles at a total fuel cost of x.
the average cost of fuel per mile is therefore x/y.
at the new cost of fuel per mile, people drove a total of (y - .067y) miles at a total fuel cost of (x + .045x) dollars.
the average cost of fuel per mile is therefore (x + .045x) / (y - .067y)
simplify the numerator and denominator and you get 1.045x / .933y.
simplify further to get the average cost of fuel per mile is 1.120042872*x/y
it looks very much like the total cost of fuel went up by 4.5% because the average cost of fuel per mile went up 12%.
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