Seemachandran, your solution requires us to assume that Bob takes the same amount of time to make the trip as Wendy. Without the statements, we know nothing about this. So he may arrive hours later or just a short time after Wendy--we have no idea. (Also, be careful with your equation: we don't want to multiply Bob's speed by (t+1/2), since he isn't walking during that half hour. His speed during that time is zero!)

Statement 1 tells us nothing about Bob, so there is no way to solve.

Statement 2 tells us that Bob is 1 mph faster than Wendy, but that's not sufficient. Here are a few possibilities:

Wendy's rate is 5 mph and Bob's is 6 mph. Her walk is 36 min and Bob's is 30 min. Since she left 30 min earlier, he arrives 24 minutes after her.

Wendy's rate is 4 mph and Bob's is 5 mph. Her walk is 45 min and Bob's is 36 min. Since she left 30 min earlier, he arrives 21 minutes after her.

More than one possibility? This is insufficient, but if we combine 1&2 we get the second possibility above. Sufficient!

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Dmitry Farber | Manhattan GMAT Instructor | New York

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