Hi All,

We're told that Greg is training for a marathon by running to and from work each day, a distance of 12 miles each way; he runs from home to work at an average speed of 6 miles per hour and returns at an average speed of 4 miles per hour. We're asked for Greg’s average speed, in miles per hour, for the round trip. This question can be solved in a couple of different ways. Sometimes the answer choices are 'spread out' in such a way that you can avoid almost all of the 'math' and use a 'logic shortcut' to get to the correct answer.

To start, since Greg is running the SAME distance in each direction, it will take him MORE time travel that distance at 4 miles/hour than it will take him to travel at 6 miles/hour. This makes this a 'Weighted Average' scenario - meaning that his average speed will be CLOSER to 4 miles/hour than it will be to 6 miles/hour. We can eliminate Answers A and B.

Since his speed never drops below 4 miles/hour, there's no way for his average speed to be less than that - so we can eliminate Answers D and E. There's only one answer remaining...

Final Answer:

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Rich

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# Rich Cohen

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