Question

What was the fastest speed of the lorry in its journey?

Give answer in Km/h and to 2 d.p

Answer 1

30 km/h

Explanation:

On a distance-time graph, the slope of the line represents the speed (the rate of change of distance with respect to time).

To find the fastest speed on a distance-time graph, we need to identify and calculate the steepest slope on the graph.

From observation of the given graph, the slope of the line is the steepest between 4 and 6 hours.

• At 4 hours, the distance travelled was 40 km.
• At 6 hours, the distance travelled was 100 km.

To find the slope of the line for this part of the journey, divide the change in distance by the change in time:

`\sf Slope\;(speed)=(100-40)/(6-4)=(60)/(2)=30\; km/h`

Therefore, the fastest speed that the lorry reached during the journey was 30 km/h.

Additional information

0 - 2 hrs: Constant speed of 20 km/h.

2 - 4 hrs: Stationary

4 - 6 hrs: Constant speed of 30 km/h.

6 - 8 hrs: Constant speed of 10 km/h.