GMAT Problem Solving (PS) | Re: Alex and Brenda both stand at point X. Alex begins to walk a

I did it this way and got the answer in less than a min.

Let's assume the value of R as 10.

So when Alex reaches 20 miles, Brenda will cover 40 miles which is what question asks.

For Alex to reach 20 mils, he needs to travel for 5 hours.

Now put the value of R in answer options and only option C will give the value as 5 hours.

This method may not work every time but sometimes it makes life easy

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