Compound Measures & Speed

• Speed = distance ÷ time, and it can be rearranged to find distance or time instead.
• A formula triangle (with Distance on top, Speed and Time on the bottom) helps you rearrange without algebra — cover up what you want, and the triangle shows you the calculation.
• Speed problems almost always involve a unit conversion — km ↔ m, hours ↔ minutes ↔ seconds. This is where most marks are lost.
• A compound measure is any quantity built from two other measurements — speed, flow rate, population density, fuel consumption, and density are all examples.
• You can work out the formula for any compound measure just by reading its units. If the unit is "a per b", the formula is (quantity a) ÷ (quantity b).
• The same formula-triangle trick works for any compound measure — not just speed. Density and pressure use the exact same structure.

Speed tells you how much distance is covered for every unit of time. That's it — that's the whole concept. If a car travels at 60 km/h, it means "for every hour that passes, this car covers 60 km." The unit itself is basically a mini-sentence: "kilometres per hour" = km ÷ h.

In real journeys, speed changes constantly (you speed up, slow down, stop at lights). So when a question says "speed," unless it specifies otherwise, it almost always means average speed — the overall rate for the whole journey, smoothing out all those changes.

Common units for speed: metres per second (m/s) for short, fast things (sprinters, cars in physics problems) and kilometres per hour (km/h) for longer journeys (road trips, flights).

If rearranging Speed = Distance ÷ Time to solve for Time or Distance feels shaky, this diagram removes the guesswork completely.

How to use it: cover up the letter you want to find with your finger. Whatever's left tells you the calculation.

• Cover Distance (top) → left with Speed and Time side by side → multiply them: Distance = Speed × Time
• Cover Speed (bottom-left) → left with Distance over Time → divide: Speed = Distance ÷ Time
• Cover Time (bottom-right) → left with Distance over Speed → divide: Time = Distance ÷ Speed

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