800score GMAT Review: Practice Math Ratio Question

800score GMAT Instructor Dr. Stergious Alexandris Yale BA, MIT PhD Math, GMAT: 800 (51 Quant , 48 Verbal) reviews the following math ratio question: When Car Z is driven at 45 miles per hour, it can travel 40 miles per gallon. But, when it is driven at 60 miles per hour it gets 20% fewer miles per gallon. How many miles does car Z traven on 10 gallons of gasoline when driven at a constant rate of 60 miles per hour?