What this guide covers
Selected Sec 1 N4 skills: average speed, rate and unit conversion. Graph-based or longer journey analysis belongs in later practice.
Total distance over total time
Average speed = total distance ÷ total time. Convert minutes to hours for kmh or to seconds for ms. A unit is part of the answer, not a decoration.
Convert time before dividing
A rider travels 1.8 km in 6 minutes. Find the average speed in kmh and ms.
- Six minutes is 0.1 hour, so speed =1.8÷0.1=18 kmh.
- Also 1.8 km=1800 m and 6 minutes=360 s, so speed =1800÷360=5 ms.
Check: 18 kmh and 5 ms describe the same speed in different units.
Try it yourself
Work on paper, then compare the steps. These checks do not establish mastery.
A runner covers 540 m in 90 s. Find the average speed in ms.
Average speed =540÷90=6 ms. Distance and time are already in the required units.
A bus covers 12 km in 20 minutes and another 18 km in 40 minutes, without stopping. Find its average speed for the full journey in kmh.
Total distance =30 km; total time =60 minutes =1 hour. Average speed =30÷1=30 kmh. The leg speeds are 36 and 27 kmh; their unweighted mean, 31.5 kmh, is not the journey average.
Where this connects
- Sec 1 rate and speed scope →
See this selected skill in the level map.
- Later: journeys with rest →
The Upper Secondary guide distinguishes moving time from elapsed time.
Sources and scope
Original Mentora examples and checks aligned to Sec 1 N4 in the MOE G2/G3 Mathematics syllabus. No school-paper item or graphic was copied.