Answer:
48 km/hr
Step-by-step explanation:
These are often calculated incorrectly because TIME is ignored
time = distance / rate
uphill = d / 40 downhill = d/60
average rate = distance / time
= 2d / ( d/40 + d/60) 2d is uphill + downhill
= 2 / ( 1/40 + 1/60 ) = 48 km/hr