Problem Solving

. A certain fraction is equivalent to . If the numerator of the fraction is increased by 4 and the denominator is doubled, the new fraction is equivalent to . What is the sum of the numerator and denominator of the original fraction?
(A) 49 (B) 35 (C) 28
(D) 26 (E) 21
ans. E
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


[spoiler]ans. B[spoiler][/spoiler


thaNKS U GUYS [/spoiler]

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


[spoiler]ans. B[spoiler][/spoiler

Let X = City MPG
Let X+6 = Highway MPG


462 Miles / x+6 MPG

336 Miles / x MPG

You can set the two equal because a tankful in the car will have an equal number of gallons.

336/x = 462/(x+6)

336x + 2016 = 462X

2016 = 126x

16 = x