Step by step
The question
Question: the distance-time graph joins (0, 0) (2, 50) (3, 50) (4, 90) (6, 90), find the speed of each part.
1 Read the graph
Across: the time in hours.
Up: how far from the start, in km.
Going up: moving away from the start.
Flat: stopped.
Going down: coming back.
2 Speed of each part
Speed is the distance divided by the time.
On the graph that is the slope: up over across.
Part A: 50 km in 2 h.
50 divided by 2 is 25 km/h.
Part B is flat.
The distance does not change: 0 km in 1 h.
The speed is 0: stopped.
Careful!
The flat part is high on the graph, but height is distance, not speed.
Flat means stopped.
Part C: 40 km in 1 h.
40 divided by 1 is 40 km/h.
Part D is flat.
The distance does not change: 0 km in 2 h.
The speed is 0: stopped.
3 Check
Let's check: speed times time gives back each distance: 50 and 40.
So it is right!
Let's look back.
First: read the graph.
Then: speed of each part.
Last: check.