Question

It took Mary 1.5 hours to bicycle 39km. Then she slowed down and took another 3 hours to bicycle 51 km more. Find her average speed for the trip.
(Total 8 points; 4 points for the answer, 2 points for the units labeled and 2 points for work shown or explanation)

Answer 1

39/1.5 = 26 km per hour
51/3 = 17 km per hour
Then you need the mean. 26+17/2 = 21.5 km per hour