Jane goes the trip of 40miles, the first 20 miles at 60 mile

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Jane goes the trip of 40miles, the first 20 miles at 60 miles per hour and the rest 20 miles at 30 miles per hour, what is the average speed of the entire trip?
A. 30miles/1hr
B. 36miels/1hr
C. 40miles/1hr
D. 42miels/1hr
E. 45miles/1hr

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by Max@Math Revolution » Sat May 14, 2016 1:50 am
Average speed = the total distance / the total time. The first 20 miles took 1/3 hr and the rest 20 miles took 2/3 hr. Then, the average speed=(20 miles + 20 miles)/(1/3 + 2/3) hr= 40 miles/1hr. Hence, the correct answer is C.