if margaret ran 8 km/h uphill for 45 minutes on her way came down at 24 km/h what was her average speed?
distance = 8 * .75 = 6 km
time down = 6/24 = 1/4 hour
total time = 3/4 + 1/4 = 1 hour
total distance = 12 km
so
average speed = 12 km/hour