Knowledge Organiser: Compound Measures
This topic summary covers Knowledge Organiser: Compound Measures within Compound Measures for GCSE Mathematics. Revise Compound Measures in Number for GCSE Mathematics with 12 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 8 of 8 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 8 of 8
Practice
12 questions
Recall
22 flashcards
Knowledge Organiser: Compound Measures
Key Terms
- Speed: Distance travelled per unit time (D ÷ T)
- Density: Mass per unit volume (M ÷ V)
- Pressure: Force per unit area (F ÷ A)
- Average speed: Total distance ÷ total time (NOT average of individual speeds)
- Formula triangle: Visual aid — cover the quantity you want to find
Must-Know Facts
- Speed: S = D ÷ T; Distance: D = S × T; Time: T = D ÷ S
- Density: D = M ÷ V; Mass: M = D × V; Volume: V = M ÷ D
- Pressure: P = F ÷ A; Force: F = P × A; Area: A = F ÷ P
- m/s to km/h: multiply by 3.6; km/h to m/s: divide by 3.6
- g/cm³ to kg/m³: multiply by 1000
- Always convert to consistent units before calculating
Key Formulas
- Speed: S = D/T
- Density: D = M/V
- Pressure: P = F/A
- Units: speed (m/s or km/h), density (g/cm³ or kg/m³), pressure (N/m² or Pa)
- 1 Pa = 1 N/m²; 1 kPa = 1000 Pa
Common Mistakes
- Formula triangle confusion: Always write D = M/V then rearrange — don't guess from the triangle
- Unit mismatch: Mixing km and m, or g and kg gives wrong answers — convert units first
- Average speed: Total distance ÷ total time (not average of two speeds)
- Time as decimals: 1 hour 30 min = 1.5 hours, NOT 1.3 hours
- Pressure area: Use consistent units — force in N, area in m² gives Pa
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Practice Questions for Compound Measures
Which formula correctly gives speed in terms of distance and time?
A car travels 80 km at 40 km/h and then 80 km at 80 km/h. Explain why the average speed for the whole journey is NOT 60 km/h.
Quick Recall Flashcards
12 questions on Compound Measures — practise free
Instant marking, adaptive difficulty, and 22 spaced repetition flashcards. Free until your GCSEs.
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