GMAT Strategy

Car B starts at point X and moves clockwise around a circular track at a constant rate of 2 mph. Ten hours later, Car A leaves from point X and travels counter-clockwise around the same circular track at a constant rate of 3 mph. If the radius of the track is 10 miles, for how many hours will Car B have been traveling when the cars have passed each other for the first time and put another 12 miles between them (measured around the curve of the track)?

Answer is 4(pi)+8.4

First eliminate the answer choices to 4pi by dividing the circumference (20pi) by 5.

Then, add the original 10 hours so you have 4pi + 10.

Then subtract 12/5 or 1.4


4pi + 10 - 1.6 = 4pi + 8.4

You have to be organized to solve this one quickly and effectively. See Image.