A man walks from B to C, a distance of x miles, at 15 miles per hour and returns at 12 miles per hour. What is his average speed?
Choose the correct choice from the following options:
A) 10 mph
B) 13 mph
C) 12 mph
D) 13.3 mph
E) 14 mph
Total distance covered = 2x   Time taken12miles / hour = x/12 hrs   Time taken @ 15 miles / hour = x/10 hrs   Avg speed = 2x / (x/15 + x/12) = 13.3 mph   Ans is 13.3 mph
<result>D</result>
A man walks from B to C, a distance of x miles, at 15 miles per hour and returns at 12 miles per hour. What is his average speed?