BTGmoderatorLU wrote: ↑

Mon May 25, 2020 6:04 am

Source: Veritas Prep

Brian takes a weekend trip to visit a friend. What is his average rate for there-and-back trip?

1. Brian took the same route for both segments.
2. Brian averaged 80 mph for the first segment and 50 mph for the second segment.

The OA is C

Let's take each statement one by one.

1. Brian took the same route for both segments.

No info abt the speed. Insufficient.

2. Brian averaged 80 mph for the first segment and 50 mph for the second segment.

We do not know whether the lengths of both segments are the same. Insufficient.

(1) and (2) together

Say the length of each segment = 400 miles (LCM of 80 and 50)

Thus, he drove for 2*400 = 800 miles

Time taken in the first segment = 400/80 = 5 hours;
Time taken in the second segment = 400/50 = 8 hours;

Average speed for the trip = 800/(5 + 8) = A unique value. Sufficient.

The correct answer: C

Hope this helps!

-Jay
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