Chapter 6.5, Problem 68E

Waste Disposal When organic waste is dumped into a pond, the oxidization process that takes place reduces the pond’s oxygen content. However, in time, nature will restore the oxygen content to its natural level. Suppose that the oxygen content t days after organic waste has been dumped into a pond is given by

$f(t)=100\left(\frac{t^2+10t+100}{t^2+20t+100}\right)$

percent of its normal level. Find the average content of oxygen in the pond over the first 10 days after organic waste has been dumped into it.