An environmental study models the concentration of a pollutant, PPP, in a stream as P=ln(0.8t)P = \ln(0.8t)P=ln(0.8t), where t>0t > 0t>0 is the time in hours after a treatment process begins. Determine the exact value of the rate of change of the concentration with respect to time at the instant when t=2.5t = 2.5t=2.5.
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.