A cyclist travels at 20 kilometers per hour when cycling uphill, 24 kilometers per hour when cycling on flat ground, and 30 kilometers per hour when cycling downhill. On a sunny day, they cycle the hilly road from Aopslandia to Beast Island before turning around and cycling back to Aopslandia. What was their average speed during the entire round trip?
Since the do an out and back trip....the up and down portions reverse and the flat remains the same
ANSWER 24 MPH
example: on the way out say 60 m up hill = 3 hours
flat 48 = 2 hrs'
down 120 = 4 hrs
on the way back up 120 = 6 hrs
flat 48 = 2
down 60 = 2 total miles 456 miles
total time = 19 hrs avg m/h = 456/19 = 24 m/hr
Thanks, EP......here's a general way of solving something like this
Assuming that the road is uphill one way and downhill the other way....we have that....
Avg rate = Total Distance / Total Time
Call the total distance = 2D
The total time is ( D/ 30) + (D /20)
So...we have that
Avg rate = ( 2D) 2D 2* 600
_____________ = ______________ = ______ = 24 mph
D/30 + D/24 D [ 30 + 20] /600 50