GregMat hard quant quiz I Doubt

GRE Quant Problem Solving
1

Hi! Doubt in this question-

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I did not follow why we are subtracting 300 here? I understand the first step- that we assumed both are starting together, and assumed 5 mins is time of meeting, and thus got 1200. Although I know the actual gap is 300 meters between them, I could not still follow the logic of how 1200-300 is accounting for that gap.

Is there any other way of thinking about this?

2

We are told to find the distance of the circular track, and not the distance between them, or the distance travelled.
If the total distance traveled is 1200, and John was already 300 meters behind, we need to subtract that to just get the total length of the circular track.

3

okay, understood, thank you

4

No problem.