This distance-time graph shows part of the journey of a boat.
What was the speed of the boat between 30 and 50 seconds after starting?
Give your answer in metres per second (m/s) and give any decimal answers to 1 d.p.
480
420-
360
300-
240
180
120
Distance travelled (m)
60
0
10 20 30 40 50 60 70 80
Time (seconds)