The idea, in short
Average speed is total distance divided by total time, never the mean of two speeds unless the times are equal. Before you divide, match every unit to the answer the question asks for: kilometres and hours for km/h, metres and seconds for m/s.
Guide · Last updated 18 Jun 2026 · Method checked by Mrs Eileen Toh, founder of Genius Plus Academy
Almost every PSLE speed question is the same rule wearing a different costume: total distance over total time. Get the units right and the rest is one division. Here are the three shapes it usually takes.
Example 1 · Convert, then divide
A walker covers 7200 m in 120 min. Find the average speed in km/h. The method is plain: convert both quantities to the units the answer needs, then divide distance by time.
\(7200\ \text{m} = 7200 \div 1000 = 7.2\ \text{km}\)
\(120\ \text{min} = 120 \div 60 = 2\ \text{h}\)
\[ \text{Average speed} = \frac{7.2\ \text{km}}{2\ \text{h}} = 3.6\ \text{km/h} \]
Answer: 3.6 km/h
See this exact question solved on video in our PSLE 2024 Paper 2 Q1 worked solution.
Example 2 · The bar model: two equal hours share the distance
Average speed is the distance covered in one hour. If the journey is 7.2 km over 2 hours, split it into 2 equal hours and share the distance equally between them. Each hour gets half.
2 equal hours share 7.2 km, so each hour covers \(7.2 \div 2 = 3.6\ \text{km}\). The distance in one hour is the speed: \(3.6\ \text{km/h}\). The bar makes it visible that "average speed" simply means "distance per single hour".
Example 3 · Comparison: who is faster, and the trap
Aiden runs 600 m in 4 minutes. Bryan runs 900 m in 5 minutes. Who runs faster? To compare, reduce each to the same unit: metres per minute.
Aiden: \(600 \div 4 = 150\ \text{m/min}\)
Bryan: \(900 \div 5 = 180\ \text{m/min}\)
Bryan is faster: 180 m/min against 150 m/min.
The trap
If one person runs a stretch at one speed and another stretch at a different speed, you cannot just add the two speeds and halve them. Average speed is the total distance over the total time. Averaging the two speed values is only correct when equal time is spent at each.
Formula quick-reference
To find speed
Speed = distance divided by time. Cover "speed" in the triangle: distance sits over time.
To find distance
Distance = speed multiplied by time. Cover "distance": speed sits beside time.
To find time
Time = distance divided by speed. Cover "time": distance sits over speed.
Common unit conversions
| 1 km | = 1000 m |
| 1 h | = 60 min = 3600 s |
| 1 min | = 60 s |
| metres to km | divide by 1000 |
| minutes to hours | divide by 60 |
| km/h to m/s | multiply by 1000, divide by 3600 (or × 5/18) |
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Same skill, different years. Each comes with a worked solution and a video.
Speed: comparing two stages of a journey.
2023 · P1 Q28Speed: short-answer rate from distance and time.
2022 · P2 Q10Speed: two travellers, comparison.
2019 · P2 Q3Speed: work backwards from the time taken.
2017 · P2 Q4Speed: model the distance with a bar.
2016 · P2 Q9Speed: bar model for distance and time.
One of the 10 question types
Once a child can read a speed question and reach for total distance over total time without hesitating, the next step is the other nine structures. Our PSLE Math Intensive drills the "Lock & Key" reflex across all ten, with 158 curated questions over two days.
Average speed is total distance divided by total time. For example, 7.2 km over 2 hours is 7.2 ÷ 2 = 3.6 km/h.
No, that is a common mistake. Average speed is always total distance over total time, not the average of two speed values, unless the time spent at each speed is equal.
Divide metres by 1000 to get kilometres, and divide minutes by 60 to get hours. So 7200 m becomes 7.2 km and 120 min becomes 2 h, which gives 3.6 km/h.
Because the units of the answer tell you the units to work in. If the question asks for km/h, you must work in kilometres and hours. Keeping metres and minutes would give an answer in m/min, which is marked wrong.
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