It takes Joey the postman 1 hour to run a 3 mile long

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It takes Joey the postman 1 hour to run a 3 mile long route every day. He delivers packages and then returns to the post office along the same path. If the average speed of the round trip is 5 mile/hour, what is the speed with which Joey returns?

A. 11
B. 12
C. 13
D. 14
E. 15

How will i start the solution to this?

OA E
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by GMATGuruNY » Mon Nov 27, 2017 3:58 am
lheiannie07 wrote:It takes Joey the postman 1 hour to run a 3 mile long route every day. He delivers packages and then returns to the post office along the same path. If the average speed of the round trip is 5 mile/hour, what is the speed with which Joey returns?

A. 11
B. 12
C. 13
D. 14
E. 15
Since Joey's average rate for the whole trip = 5 mph, and the total distance back and forth = 6 miles, Joey's total time for the whole trip = d/r = 6/5 hours.
Since his delivery time = 1 hour, his return time = (total time) - (delivery time) = (6/5) - 1 = 1/5 hour.
Thus, Joey's rate when he returns to the post office = (return distance)/(return time) = 3/(1/5) = 15mph.

The correct answer is E.
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by Scott@TargetTestPrep » Mon Oct 07, 2019 10:17 am
BTGmoderatorDC wrote:It takes Joey the postman 1 hour to run a 3 mile long route every day. He delivers packages and then returns to the post office along the same path. If the average speed of the round trip is 5 mile/hour, what is the speed with which Joey returns?

A. 11
B. 12
C. 13
D. 14
E. 15

How will i start the solution to this?

OA E
We can let r = Joey's speed for the return trip and create the rate equation:

5 = 6/(3/3 + 3/r)

Multiplying the right hand side by r/r, we have:

5 = 6r/(r +3)

5r + 15 = 6r

15 = r

Answer: E

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