One model of Earth's population growth is http://i.imgur.com/AZ7d8Bv.png, where t is measured in years since 1990, and P is measured in billions of people. Which of the following statements are true?

Check all that apply.
The carrying capacity of Earth is 5.33 billion people.

In 1990, there were 5.33 billion people.

The population of Earth will grow exponentially for a while but then start to slow down its growth.

The population of Earth is increasing by a steady rate of 8% per year.

Question

One model of Earth's population growth is http://i.imgur.com/AZ7d8Bv.png, where t is measured in years since 1990, and P is measured in billions of people. Which of the following statements are true?

Check all that apply.
        The carrying capacity of Earth is 5.33 billion people.

        In 1990, there were 5.33 billion people.

        The population of Earth will grow exponentially for a while but then start to slow down its growth.

        The population of Earth is increasing by a steady rate of 8% per year.

anonymous · Answer

I think its d and c

b87lar · Answer

(b) and (c) 
for b: set t=0 (year 1990) you will get 5.33 (pop in billions in 1990)
for c: for rel. small t the exp function dominates the denominator. Since it has negative power you can view it as exponential in the numerator and hence the growth can be called approximately exponential. As t gets larger this this trend attenuates and the growth becomes flat. (whic, btw., makes the statement (d) incorrect!)