Question

At the beginning of environmental study, a forest covered an area of 1500km2. Since then, this area has decreased by 8.6% each year.

Let t be the number of years since the start of the study. Let y be the area that the forest covers in km2.

Write an exponential function showing the relatishionship between y and t.

Answer 1

First we need to change a decline of 8.6% to a decimal, which is 0.914 (100% - 8.6%). With an initial value of 1500 we get:

$y = 1500 \times 0.914 {}^{t}$