Me:
in 1990, the rate of change of the world population was approximately 0.09125 billion per year (or approximately 1 million people every four days). the world population was estimated to be 5.3 billion in 1990.

according to the model, when will the population of the world be double the 1990 population?

a. the population will double in approximately 270 years time, by 2260.
b. the population will double in approximately 17 years time, by 2007.
c. the population will double in approximately 58 years time, by 2048.
d. the population will double in approximately 116