The road from AtoB is 10km uphill followed by 20km downhill. A motorcyclist average 36km/hr uphill and 90km/hr downhill. Calculate the average speed? (a) from A to B (b) from B to A.
OMG, what a gobble-de-goop by the bot
a) total time = 10hr/36 mph + 20hr/90mph = 1/2 hour
avg speed = total distance / total time
= 30 mi/(1/2 hr) = 60 mph
b) assumption would be that the uphill would now become the downhill and
vice versa.
avg speed = 30/(20/36 + 10/90) = 30/(2/3) = 45 mph
(a) Average speed from A to B:
(10 km/hr uphill + 90 km/hr downhill) / 2 = 50 km/hr
(b) Average speed from B to A:
(36 km/hr uphill + 20 km/hr downhill) / 2 = 28 km/hr