Miles per gallon!

[GMAT08]

Q. A car traveled 462 miles per tankful of gasoline on the highway and 336 miles per tankful of gasoline in the city. If the car traveled 6 fewer miles per gallon in the city than on the highway, how many miles per gallon did the car travel in the city?
(A) 14
(B) 16
(C) 21
(D) 22
(E) 27
Pls explain! Thx

[Dynamo]

IMO B 16

Let the capacity of tank be x gallon

from the question

462/x - 336/x = 6

x = 21

therefore rate in the city = 336/ 21 = 16

what is the Official Answer?

[Lhomme]

say car drives x gallons/mile on highway and y gallons/mile on city.

Let the capacity of car be c gallons.

hence we have
x = 336/c and y = 462/c

We have been given that car drives at 6 fewer miles per gallon on city comparerd to highway. converting this to equation

x = y -6

336/c = 462/c -6

solving for c we get, c = 21.

Hence, put valkue of c to get value of x.

x = 336/c = 336/21 = 16.

Answer is 16.

Official Answer- B

[GMAT08]

Thanks! Very helpful. Official Answer is B. I got X and forgot to complete the question by 336/x to get the mpg in the city! Doh!