Applications of Derivatives · Theorems

Related Rates

ddt[equation] -differentiate both sides with respect to time\frac{d}{dt}[\text{equation}] \text{ -differentiate both sides with respect to time}

Related rates problems involve finding how fast one quantity changes given how fast another changes. Differentiate an equation relating the quantities with respect to time.

  • 0 variables
  • 2 worked examples
  • 15 in Applications of Derivatives

Worked examples

A circle has radius growing at 2 cm/s. Find dA/dt when r = 5 cm.
  1. A = πr². Differentiate: dA/dt = 2πr · dr/dt
  2. dA/dt = 2π(5)(2) = 20π

Answer: dA/dt = 20π ≈ 62.83 cm²/s

1 more worked examplePremium

A 10-ft ladder slides down a wall. The base moves at 1 ft/s. How fast does the top slide when the base is 6 ft from the wall?

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Practice

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