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Jim and Mike stand at point P. Jim begins to cycle in a straight line away from Mike at a constant rate of 3 mph. Two hours later, Mike begins to run in a straight line in the exact opposite direction at a constant rate of 2 mph. If both Jim and Mike travel indefinitely, what is the positive difference, in minutes, between the amount of time it takes Mike to cover the half distance that Jim has covered and the amount of time it takes Jim to cover four times the distance that Mike has covered?
A. 84
B. 144
C. 240
D. 300
E. 336
In two hours, Jim travels 6 miles. Then Mike starts moving. So t hours after that, Jim has traveled 6 + 3t miles, and Mike has traveled 2t miles. If we need Mike to cover half the distance Jim covers, we need the ratio of these distances to equal 1/2, so
2t / (6 + 3t) = 1/2
4t = 6 + 3t
t = 6
That's in hours, so it takes 360 minutes.
If instead we Jim to have traveled 4 times as far as Mike, we want the ratio of Jim's distance to Mike's distance to be 4/1, or 4, so we have
(6 + 3t)/2t = 4
6 + 3t = 8t
6 = 5t
t = 6/5
and since that's in hours, it takes 1 and 1/5 hours, or 72 minutes.
edit: as caubesaokim1993 points out, in this step the question asks for the time Jim takes, not the time Mike takes, so we need to add the 2 hour head start that Jim got, and this time is 192 minutes. I neglected to do that in my first reply, so I've edited the last step:
The positive difference of these two times is 360 - 192 = 168 minutes.
That doesn't seem to be among the answer choices. I suppose it's possible I've misinterpreted the meaning of the question, since there are many issues with the wording, but I can't guess how I might have done that. What is the source?