Question

Which equation represents a population of 320 animals that decreases at an annual rate of 19% ?

A. p=320(1.19)t
B. p=320(0.81)t
C. p=320(0.19)t
D. p=320(1.81)t

Answer 1

Answer: Choice B. p = 320(0.81)^t

Use the ^ symbol to indicate exponents. So for instance 4^2 = 4 squared.

A decrease of 19% means we have r = -0.19 and 1+r = 1+(-0.19) = 0.81 as the base of the exponent. A decrease of 19% means the population retains 81% each year.