Jack is at (2/3) of the length of the beach (measuring from the point where they started).
Let's think that the whole beach is like a line track of length L.
We know that when Jill completes reaches the end (one complete run) Jack only completed half of it.
So in the time that jill covers the distance L, Jack covers a distance of L/2. So the ratio of their speeds is 2:1 (Jill's speed is double of Jack's speed).
At this point, Jill is on the end of the track and Jack is on the middle, so the distance between them is L/2.
Because of the ratios between the speeds, we know that when they meet again, Jill will have covered 2 thirds of that distance, and jack will cover the other third of that distance.
A third of that distance is:
(L/2)/3 = L/6
So, when they meet, Jack is at L/6 of the middle of the beach, which means that Jack is:
L/2 + L/6 = 3L/6 + L/6 = 4L/6 = 2L/3
Jack is at (2/3) of the length of the beach (measuring from the point where they started).
If you want to learn more about distances:
https://brainly.com/question/4931057
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