There are 450 litres of water in a pond and 8 litres of water evaporate out of the pond every hour. After how many hours will the pond be empty?
I've already figured out an equation for the question which is, A=450-8h, A being the pond and h being hours but I'm not sure how to use that.
\begin{align} A(x) = 450 - 8x, x \in [0, +\infty] \end{align} since there are no negative hours. In order to find out when it will empty, just set \begin{align} A(x) = 0\\ \implies 450 - 8x = 0\\ \implies 450 = 8x\\ \implies x = \dfrac{450}{8}\\ \implies x = 56.25. \end{align} Thus the pool will empty in 56 and a quarter hours.
