A certain forest covers an area of 3900 km^2. Suppose that each year this area decreases by 5.5%. What will the area be after 15 years?

Hey there!

To start, this is an exponential, meaning your equation should be in this format:

y=a (1±b) ^x where a is the principal amount, b is the rate, and x is the years passed. If b is a decrease rate, you would subtract it from one, and if it is an increase rate, you would add it to 1. In this case, the rate 5.5% is a decrease rate so you would perform 1-5.5% or 1-0.055 which would be 0.945.

Now, plug in your known values:

y=3900 (0.945) ^15

Finally, simplify to get:

y=1669.33

Now, round to the nearest whole number (you can't have a decimal of a tree) to get 1669 trees after 15 years.