The population P P\,P of a colony is measured in thousands and time t t\,t is measured in years. Without intervention, the rate of increase of the population is proportional to PPP. When P=4P=4P=4, the population is increasing at 0.12 thousand per year.
Construct a differential equation for P P\,P in the form
dPdt=kP\dfrac{dP}{dt}=kPdtdP=kP,
and find kkk.
The colony is then harvested continuously at a constant rate of 0.10 thousand per year.
Construct the new differential equation.
According to this model, determine the range of values of P P\,P for which the population is decreasing.
263 exam-style questions on CCEA A Level Maths 3.5 Differentiation (A-level only), covering 3.5.1 Differentiation (A-level only), 3.5.2 Differentiation (A-level only), 3.5.3 Differentiation (A-level only), 3.5.4 Differentiation (A-level only), 3.5.5 Differentiation (A-level only), and 3.5 Differentiation (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.