Bill started walking with a speed of X miles per hour

[himalayanmonk]

Bill started walking with a speed of X miles per hour.
Will he cover more than 16 miles in the next 8 hours ?

1. In 2 hours he will cover 4 miles.
2. In 5 hours he will covers at most 10 miles.


I have two specific queries.
A. In case of time-speed-distance(TSD) problems is it mandatory to have average explicitly mentioned ?
B. If it is not mandatory then we can say that in 8 hours Bill will cover exactly 16 miles. So in this case option 1 is sufficient as well. However had we had the phrase "At least" in option 1, we could have said that option 1 is insufficient. So my question is in case of absence of the indicators such as average should we consider that somebody/something(here Bill) is moving with an average speed ?

Thanks in advance.

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Hi himalayanmonk,

What is the source of this question? I ask because the wording isn't quite up to the 'standard' that you'll find in Official GMAT questions. If other prompts from this source are written in the same sloppy fashion, then you might want to practice with more reputable material.

In this prompt, the 'intent' is to test your understanding of average speed, but the wording of the first Fact is open to some interpretation.

In Fact 1, we're left to interpret whether the wording means "in the first 2 hours he will cover 4 miles" OR "every 2 hours he will cover 4 miles"

Depending on your interpretation, Fact 1 is either sufficient OR insufficient. The GMAT has a rigorous testing process to 'weed out' questions that have interpretational bias, so you wouldn't see a question written in this way on Test Day.

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

[Matt@VeritasPrep]

This would be E. You can't assume that Bill will walk at a constant rate, so you don't know how far he'd walk.

The GMAT itself will be explicit about whether the rate is constant (or whether you should only consider the AVERAGE rate, which works out about the same).