Hi erikvm,
This question relates the speed of the walker to that of the jogger, so we can use 1 variable to refer to both.
Speed of Walker: X miles/hour
Speed of Jogger: (2X-1) miles/hour
Now we can use the distance formula (we were told that the length of time is 2 hours for each person):
(Rate)(Time) = Distance
Walker: (X miles/hour)(2 hours) = 2X miles
Jogger: (2X-1 miles/hour)(2 hours) = (4X - 2) miles
We're also told that, after those 2 hours, the jogger is 3 miles ahead of the walker, so the difference in distance can be represented as.....
(4X - 2) - 2X = 3 miles
Now we simplify....
2X - 2 = 3
2X = 5
X = 2.5
This means that the speed of the Walker is 2.5 miles/hour and the speed of the Jogger is 2(2.5) - 1 = 4 miles/hour
With these numbers, we can actually 'double check' the math....
Walker: (2.5)(2) = 5 miles
Jogger: (4)(2) = 8 miles
Difference = 3 miles, which is a match for what we were told.
GMAT assassins aren't born, they're made,
Rich
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