Hi viktorija,

BassanioGratiano has shown how TESTing THE ANSWERS can be used to solve this problem. Here's another pattern-based approach.

This prompt describes the paths traveled by 2 trucks - if you were to draw a series of pictures that were based on the distances and speeds described over time (from 1pm onward), you would end up with a series of RIGHT TRIANGLES.

The GMAT commonly tests a set of established right triangles - 30/60/90, 45/45/90, 3/4/5 and 5/12/13. Here, we're asked for the time at which the trucks are 10 miles apart. Since the question doesn't describe angles of any kind, and 10 is a multiple of 5, we're almost certainly looking for a 3/4/5 triangle that's been doubled (into a 6/8/10 triangle).

At 1:00pm, Truck A is 14 miles NORTH of Truck B. Truck A is traveling SOUTH, Truck B is traveling East - they're both traveling 30miles/hour. This means that every 2 minutes = 1 mile traveled.

We can now make a quick table comparing the "sides of the triangle" that would be created by the two trucks:

A|B

13|1 Not a 6/8/10

12|2 Not a 6/8/10

11|3 Not a 6/8/10

10|4 Not a 6/8/10

9|5 Not a 6/8/10

8|6 !!!!!This IS a 6/8/10!!!!!!

Since each Truck traveled 6 miles, and 1 mile = 2 minutes, we know that the trucks traveled 6(2) = 12 minutes. At 1:12pm, the trucks are exactly 10 miles apart.

Final Answer:

GMAT assassins aren't born, they're made,

Rich

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