Graphs of velocity versus time are shown below for a car and a motorcycle travelling along the same road. The car passes the stationary motorcycle at t = 0.

What is the average acceleration (in km/h/s) of the motorcycle during the first 15 seconds?

a = Δv/Δt = 100/15 = 6.67 m/s^{2}= 24km/h/s

At what time does the motorcycle overtake the car?

I figured that the point at which their distances are equal is when the motorcycle overtakes the car, and as such did (using the average acceleration above):

d(motorcycle) = 3.33t^{2 }

d(car) = vt = 22.22t

3.33t^{2}= 22.22t

t = 6.7 seconds