The rate r at which people get sick during an epidemic of the flu can be approximated by r = 1600te-0.2t where r is measured in people/day and t is measured in days since the start of the epidemic.

Given 100 grams of bacteria that decreases at a rate of 1/2 per year. What would be an appropriate range after 4 years?

The relationship between the volume, V, measured in cm³, of a balloon and the internal air pressure, P, measured in grams/cm², is given by PV = 45 000. The volume of a balloon is increasing at a rate of 100 cm³s-1. Find the rate of change of the air pressure inside the balloon when the volume is 4 000 cm³.