OCR MEI Paper 3 2020 November — Question 7

Exam BoardOCR MEI
ModulePaper 3 (Paper 3)
Year2020
SessionNovember
TopicFirst order differential equations (integrating factor)

7
  1. Express \(\frac { 1 } { x } + \frac { 1 } { A - x }\) as a single fraction. The population of fish in a lake is modelled by the differential equation
    \(\frac { d x } { d t } = \frac { x ( 400 - x ) } { 400 }\)
    where \(x\) is the number of fish and \(t\) is the time in years.
    When \(t = 0 , x = 100\).
  2. In this question you must show detailed reasoning. Find the number of fish in the lake when \(t = 10\), as predicted by the model.