Question

In 1990, the population of Area A was about 60 miltion. During the 1990s, the population of this area increased an average of about 0.4 million per year The population of Area B was a bout 53 million in 1990. The population of this area increased an average of about 1 milion per year during the 1990s. Assume that the rate of growth of these areas remains the same. Estimate when the population of the Area B would be equal to the population of the Area A

Answer 1

The difference in population at the start of the decade is 60-53=7 million. The growth of Area B is 1-0.4 = 0.6 million per year faster than for Area A. Each year, the difference in population gets smaller by 0.6 million, so the difference of 7 million will disappear in 7/0.6 ≈ 11.7 years, late in the year 2001.