The annual birth and death rate in a country per 1000 are 39.4 and 19.4 respectively . the number of years R in which the population would be doubled assuming there is no emigration or immigration is Choices
A) 20  B) r = 25  C) r = 30  D) r = 35  E) 40

Rationale: "suppose the population of the country in current year is 1000 . so annual increase is 1000 + 39.4 - 19.4 = 1020 hence every year there is an increase of 2 % . 2000 = 1000 ( 1 + ( 2 / 100 ) ) ^ n n = 35 answer is d ."
Answer: D