Exponential

Problem:

 

Solution: 

a) The two year growth rate can simply found by division

$ \frac{3715.2}{2580} = 1.44 $

You should find the same value for all adjacent values in the table.

b) You take square root of that to find the 1 year growth rate

$ \sqrt{1.44} = 1.2 $.

That means it is increasing by 20% every year.

c) We go backwards to find that, let that quantity be x

The weight of garbage is 1985 is 2580 (1 year since 1984 is 1985)

Now, $ x \times 1.2 \times 1.2 \times 1.2 = 2580 $, so $ x = 1493.056 $.