Distance-time graph: (0, 0) (1, 50) (3, 50) (4, 0), find the speed…

Step by step, with the reason for every step · Distance-time graphs · Algebra 1

Step by step

Question: the distance-time graph joins (0, 0) (1, 50) (3, 50) (4, 0), find the speed of each part.

distance-time graph: (0, 0) (1, 50) (3, 50) (4, 0)

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.

Speed is the distance divided by the time.

On the graph that is the slope: up over across.

speed = distancetime = slope

Part A: 50 km in 1 h.

50 divided by 1 is 50 km/h.

A: speed = 501 = 50 km/h

Part B is flat.

The distance does not change: 0 km in 2 h.

The speed is 0: stopped.

B: speed = 02 = 0 km/h

Careful!

The flat part is high on the graph, but height is distance, not speed.

Flat means stopped.

Careful: not speed = 50 km/h ✗

Part C: 50 km in 1 h, coming back.

50 divided by 1 is 50 km/h.

C: speed = 501 = 50 km/h

Let's check: speed times time gives back each distance: 50 and 50.

So it is right!

50 × 1 = 50, 50 × 1 = 50

Let's look back.

First: read the graph.

Then: speed of each part.

Last: check.

Answer

C: speed = 501 = 50 km/h

Try this one yourself, then check:

distance-time graph: (0, 0) (1, 25) (3, 25) (4, 0)

Show the answer

A: 25 km/h, B: 0 km/h, C: 25 km/h