Bunuel
A gas station sells three grades of fuel High, Medium and Low. The selling price of High grade is $2.20 per gallon, which is 25 percent higher than that of Medium grade, while the price of Low grade is 75 percent of the selling price of Medium grade. If on a given day the station sells twice as much Low grade gas as Medium grade gas, and 4 times as much Medium grade gas as High grade gas, with total revenue of $99, how many gallons of fuel did the station sell?
A. 130
B. 91
C. 78
D. 65
E. 39
As word problems can be confusing, we'll use the answers!
This is an Alternative approach.
We'll start with the median answer - C.
Since the ratio between gallons sold is 1:4:8 then each ratio unit is 78/13 = 6 gallons of gas.
Then the total revenue is
6*2.2 + 24*0.8*2.2 + 48*0.8*0.75*2.2 =
2.2*6(1+ 4*0.8 + 8*0.8*0.75) =
13.2(1+3.2+4.8) = 13.2*9 which is about 120.
Too much! (C) and the larger (B), (A) are eliminated.
Moreover, since (E) would mean decreasing the revenue by half, we know that it must be too small.
Then we can mark (D) and move on.
Just for practice, since 65/13 = 5, we can use our simplification from above to write:
2.2*5*9 = 11*9 = 99, as required.