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