Speed is an example of a compound measure, which is one that involves more than one unit of measurement.
Speed is a measure of distance (e.g. miles, km) in relation to time (e.g. hours, minutes) and can be measured in mph (miles per hour), km/h etc.
Throughout a typical journey, speed varies. It stays constant, then it may increase or decrease.
We calculate the average speed from the total distance travelled and the total time taken.
Average speed = total distance travelled ÷ total time taken
A train leaves London at 11:30 and arrives in Portsmouth at 12:20.
The distance between the two stations is 110 km.
Find the average speed in km/h.
First, we must state the time taken in hours, not in minutes.
Time taken = 50 minutes = 50/60 which is simplified to 5/6 hour.
Average Speed = total distance ÷ total time
= 110 ÷ 5/6
= 110 × 6/5
= 132 km/h
The average speed is 132 km/h
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