(A Math) 2025 CCHY PRELIMS P2 Q1

(A Math) 2025 CCHY PRELIMS P2 Q1

Secondary 4
5 marks

In 2020, there were an estimated 7 million insects of a particular species in a certain country. In 2021, the numbers were estimated to have fallen to 5 million. Scientists believe that the number of these insects, \(N\) million, can be modelled by the formula \(N = 3 + ae^{-kt}\), where \(t\) is the time in years after 2020.

  1. Find the exact values of \(a\) and of \(k\).[4]
  2. What is the approximate size of the population for large values of \(t\)?[1]

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Answer:(a) \(a=4\), \(k=\ln2\) (b) \(3\) million insects

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