The depth of water in an experimental filtration vessel, D D\,D centimetres, varies according to the radius of the sediment layer r r\,r millimetres, such that D=(2r3+9r2)4D = (2r^3 + 9r^2)^4D=(2r3+9r2)4. Determine the rate of change of the depth with respect to the radius, dDdr\displaystyle \frac{dD}{dr}drdD.
717 exam-style questions on Edexcel A Level Maths Differentiation, covering 9.1 Differentiating sin x and cos x, 9.2 Differentiating exponentials and logarithms, 9.3 The Chain Rule, 9.4 The Product Rule, 9.5 The Quotient Rule, 9.6 Differentiating Trigonometric Functions, 9.7 Parametric Differentiation, 9.8 Implicit Differentiation, 9.9 Using Second Derivatives, and 9.10 Rates of Change. Each one has a worked solution and a mark scheme showing where the marks go.