M7MBA wrote:If it took a bus 4 hours to get from town A to town B, what was the average speed of the bus for the trip?

(1) In the first 2 hours, the bus covered 100 miles.
(2) The average speed of the bus for the first half of the distance was twice its average speed for the second half.

[spoiler]OA=E[/spoiler]

Source: GMAT Club Tests

Let's take each statement one by one.

(1) In the first 2 hours, the bus covered 100 miles.

We do not have information about how many miles the bus took in the second 2 hours. Insufficient.

(2) The average speed of the bus for the first half of the distance was twice its average speed for the second half.

Say the average speed of the bus for the second half was x mph; thus, the average speed of the bus for the first half would be 2x mph. Say the distance from A to B is 2d miles.

Thus, the total time taken by bus = d/2x + d/x = 3d/2x hours

Thus, the average speed of the trip = (Distance from A to B) / (the average speed of the trip) = 2d/(3d/2x) = 4x/3 mph

Since we do not have the value of x, we can't get a unique answer. Insufficient.

(1) and (2) together

From (1) and (2), we cannot assume that 100 miles is the first half of the distance or d = 100. Thus, even both statements together are insufficient.

The correct answer: E

Hope this helps!

-Jay
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