SOLUTION: there's an army 5 miles long marching at 3 mph your in front and you have to take a letter 5 miles to back of the line at 5 mph and return to the front at 5 mph how many miles and
Question 573120: there's an army 5 miles long marching at 3 mph your in front and you have to take a letter 5 miles to back of the line at 5 mph and return to the front at 5 mph how many miles and how many hours did it take Found 2 solutions by solver91311, Alan3354:Answer by solver91311(24713) (Show Source):
When you start, the rear of the army is APPROACHING you at 3 mph and you are traveling 5 mph for a total rate of 8 mph. Using time equals distance divided by rate, it takes you 5/8 of an hour to get to the rear of the column.
On the way back, the front of the army is moving AWAY from you at 3 mph and you are traveling 5 mph for a total rate of 2 mph. T = D/R again, so 5/2 hour to get back to the front.
You can do your own arithmetic.
John
My calculator said it, I believe it, that settles it
You can put this solution on YOUR website! there's an army 5 miles long marching at 3 mph your [sic] in front and you have to take a letter 5 miles to back of the line at 5 mph and return to the front at 5 mph how many miles and how many hours did it take
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The round trip distance is 10 miles.
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The relative speed going is 3 + 5 = 8 mi/hr
Returning it's 5 - 3 = 2 mi/hr
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The avg speed for the round trip is
2*8*2/(8 + 2) = 3.2 mi/hr
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t = d/r = 10/3.2 = 3.125 hours
