Inequalities Problem Solving: GMAT, GRE

GMAT, GRE MPG Conversion Problem

A car gets 30 miles to the gallon. If it is modified to use a solar panel, it will use only 75 percent as much fuel as it does now. If the fuel tank holds 15 gallons, how many more miles will the car be able to travel, per full tank of fuel, after it has been modified?

A. 112.5
B. 150
C. 337.5
D. 450
E. 500

GRE, GMAT Work Problem with Remainders

Machine A and Machine B can produce 1 widget in 3 hours working together at their respective constant rates. If Machine A's speed were doubled, the two machines could produce 1 widget in 2 hours working together at their respective rates. How many hours does it currently take Machine A to produce 1 widget on its own?

A. 1/2
B. 2
C. 3
D. 5
E. 6