Let's begin with the following graph. We can see that the motion shown by the yellow line is fastest.
By definition, speed = distance / time so the steepness (or gradient) of the line will give us the speed! Yellow: speed = distance / time = 30 m / 10 s = 3 m/s Blue: speed = distance / time = 20 m / 20 s = 1 m/s
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