A zoologist is investigating the growth of a population of red squirrels in a forest - AQA - A-Level Maths Pure - Question 2 - 2017 - Paper 2

To find the size of the squirrel population at the start of the investigation, we need to evaluate the equation when time t is 0.
Substituting t = 0 into the equation gives us:
$N = \frac{200}{1 + 9e^{-\frac{0}{5}}}$
This simplifies to:
$N = \frac{200}{1 + 9e^{0}} = \frac{200}{1 + 9 \cdot 1} = \frac{200}{10} = 20$
Therefore, the size of the squirrel population at the start of the investigation is 20.