Question

The number of birds in a forest is decreasing by 3% every year. In 2000 there were 5,400 birds. Write an equation that represents the number, y, of birds x years after 2000. How many birds will there be in 2025? Round your answer to the nearest whole number.

Answer 1

Explanation:

This is a Compound interest problem with a decreasing rate. It is given by the formula:

A = P(1 +/- R)^T

Where A = amount after time T

P = principal or initial amount

R = rate of increase or decrease

T = time elapsed

There's +/- because + is used in the case when the amount is increasing at a particular rate and - is used whe the amiunt is decreasing.

In 2000 there were 5,400 birds and the number of birds is decreasing by 3% (0.03) every year.

The number of birds, y, that will be there x years after 2000 will be:

y = 5400( 1 - 0.03)ˣ

2025 is 25 years ahead of 2000, so x = 25

Therefore, the number of birds in 2025 will be:

y = 5400(1 - 0.03)^25

y = 5400(0.97)^25

y = 5400 * 0.467

y = 2522 birds

There will be 2522 birds in 2025.