Hi lheiannie07,

This prompt gives us a lot of different facts about rates, times and distances, so we're clearly going to use the distance formula here:

Distance = (Rate)(Time)

We're looking for the time at which the distance between the two drivers was 240 miles - and since the answer choices are 5 times, we can use them 'against' the prompt and TEST THE ANSWERS.

Let's Test Answer B: 2:00pm
At 2pm....
Ben would have been driving for 6 hours at 20 miles/hour = 120 miles driven
Al would have been driving for 3 hours at 40 miles/hour = 120 miles driven
Total Distance = 120 miles + 120 miles = 240 miles
This is an exact MATCH for what we were told, so this MUST be the answer!

Final Answer: B

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

BTGmoderatorDC wrote: ↑

Mon Sep 11, 2017 1:57 pm

Al and Ben are drivers for SD Trucking Company. One snowy day, Ben left SD at 8:00 a.m. heading east and Al left SD at 11:00 a.m. heading west. At a particular time later that day, the dispatcher retrieved data from SD's vehicle tracking system. The data showed that, up to that time, Al had averaged 40 miles per hour and Ben had averaged 20 miles per hour. It also showed that Al and Ben had driven a combined total of 240 miles. At what time did the dispatcher retrieve data from the vehicle tracking system?

A. 1:00 p.m.
B. 2:00 p.m.
C. 3:00 p.m.
D. 5:00 p.m.
E. 6:00 p.m.

How will i start solving it? What formula will i use? Can any experts help?

OA B

Let t represent the time that passed between the departure of Al (11:00 a.m.) and the retrieval of data by the dispatcher. Since Ben left at 8 a.m., his time is (t + 3). Since their combined distance was 240 miles, we can use the formula distance = rate x time and create the following equation:

Ben’s distance + Al’s distance = 240

20(t + 3) + 40t = 240

20t + 60 + 40t = 240

60t = 180

t = 3 hours

Thus, it was 11 a.m. + 3 hours = 2 p.m. when the dispatcher retrieved data from the vehicle tracking system.

Answer: B