MATHEMATICS

Question

the number of trees in a rain forest decreases each month by 0.5%. If the forest has approximately 2.34 •10^9 trees, how many trees will be left after 20 years?

Answer 1

If we decrease by 0.5% per month, then each month the number of trees is

99.5% of the previous month.

 

P(t) = P₀(0.995)^t

P(t) is number of trees at time t months

P₀ = initial number =  2.34 •10^9

t = number of months = 20(12) = 240

 

p(20) = 2.34(10⁹)(0.995²⁴⁰) = .70268 x 10⁹ = 7.0268 x 10⁸