(c) One lorry travels from your town to another town. The lorry reaches a top speed of 90 km/h, but its average speed between the towns is only 66 km/h.
Why is the average speed less than the top speed?

The average speed is 24 km/h less than the top speed of the lorry.

Step-by-step explanation:

The top speed of the lorry is the highest speed reached during transit, while its average speed is the mean speed attained

Given:.

Top speed of the lorry = 90 km/h

Average speed of the lorry = 66 km/h

Then,

The difference between the speed reached = top speed - average speed

                                            = 90 - 66

                                            = 24 km/h

Therefore, the average speed is 24 km/h less than the top speed of the lorry.

are you sure this is middle schools math? ?