How do I find average velocity without being given distance or time?

Question

The problem for my homework is: "A car travels up a hill at a constant speed of 44 km/h and returns down the hill at a constant speed of 67 km/h. Calculate the average speed for the round trip".

Answer 1

A short cut to this problem is to note that the length of the hill does not matter. Regardless of the length of the hill the average speed will be the same. Thus one can just pick the length of the hill to be 10 km

Then: time_up = 10 / 44 and time_down = 10/67

The average speed is (10 + 10 ) /(time_up + time down)

Plugging in one gets average speed = 5896/111 = 53.117 km/hr