Paper 1 · Differentiation ⏱ Tested in 5+ recent exam questions Lesson 20 of 21

Differentiation 20 – Rate Problems

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You’ll learn

  • Solve related-rates problems with the chain rule, e.g. dR/dt = (dR/dV)·(dV/dt)
  • Use the reciprocal trick dR/dV = 1/(dV/dR) when the formula gives V in terms of R
  • Eliminate a variable with similar triangles before differentiating cone problems
  • Identify the given and required rates and state units (cm/s, cm²/s, cm³/s)

Most recent exam questions

  • 2025 P1 Q9(a)(v)
  • 2025 P1 Q9(b)(ii) — deferred
  • 2024 P1 Q9(d)
  • 2024 P1 Q9(e)(ii) — deferred
  • 2023 P1 Q10(b) — deferred

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