BTGModeratorVI wrote: ↑Sat Mar 21, 2020 9:48 am
Triathlete Dan runs along a 2-mile stretch of river and then swims back along the same route. If Dan runs at a rate of 10 miles per hour and swims at a rate of 6 miles per hour, what is his average rate for the entire trip in miles per minute?
A. 1/8
B. 2/15
C. 3/15
D. 1/4
E. 3/8
Answer:
A
Source: Manhattan Prep
We can use the average rate formula: average rate = total distance/total time. We see that the total distance is 4 miles. The total time for swimming is (2 miles)/(6 miles per hour) , and the total time for running is (2 miles)/(10 miles per hour). Thus, we have:
average rate = 4/(2/6 + 2/10)
average rate = 4/(1/3 + 1/5)
average rate = 4/(5/15 + 3/15)
average rate = 4/(8/15) = 60/8 mph
Since 1 hour = 60 minutes, then 60/8 mph = 60 mi/8 hr x 1 hr/60 min = 1/8 mi/min.
Answer: A
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