Hi All,
We're told that both car A and car B set out from their original locations at exactly the SAME time and on exactly the SAME route. Car A drives from Morse to Houston at an average speed of 65 miles per hour and Car B drives from Houston to Morse at 50 miles per hour, and then immediately returns to Houston at the same speed and on the same route, arriving in Houston 2 hours after car A. We're asked how many hours it took car A to make its trip. This question can be solved in a couple of different ways, including by TESTing THE ANSWERS. Let's TEST Answer B first...
Answer B: 1 hour
If Car A travels for 1 hour, then it travels (1)(65) = 65 miles, meaning that the distance between the two cities is 65 miles.
Car B would have to travel 65+65 = 130 miles at 50 miles/hour.
130 miles = (50 mph)(T hours)
130/50 = T
2.6 hours = T
This is 2.6 - 1 = 1.6 hours after Car A arrived, but this is NOT a match for what we were told (it's relatively close, but it's supposed to be a 2 hour difference). Thus, we need the distance between the cities to be LARGER (but not too much larger).
Answer C: 1.25 hours
If Car A travels for 1.25 hours = 5/4 hours, then it travels (5/4)(65) = 325/4 = 81.25 miles, meaning that the distance between the two cities is 81.25 miles.
Car B would have to travel 81.25 + 81.25 = 162.5 miles at 50 miles/hour.
162.5 miles = (50 mph)(T hours)
162.5/50 = T
3.25 hours = T
The difference is 3.25 - 1.25 = 2 hours. This is an exact match for what we were told, so this must be the answer.
Final Answer: C
GMAT assassins aren't born, they're made,
Rich
