math
posted by jake .
If a hiker walks trail B (1 mile in length) at 6 mph and trail C (3 mils in length) at 2 mph, what is the hiker's overall average speed, in mph, for hiking on the two trails?

time for trail B = 1/6 hrs
time for trail C = 3/2 hrs
total time = 1/6 + 3/2 = 5/3 hrs
avg speed = total distance / total time
= 4/(5/3) = 4(3/5) = 12/5 mph or 2.4 mph