Question

For country A, the population in 2000 was 1 billion. It has reached 2 billion in 2020. For country B, the population in 2000 was 160 million. It has reached 800 million in 2020. Which country will have a larger population by the end of 2030, assuming the population fold change is the same?

(a) Country A will be more populous compared to Country B

(b) Country B will be more populous compared to Country A

(c) Both countries A and B will have the same population

(d) Country A will be more populous compared to Country B

I got this question in an interview for job.

The question is from Reproductive Health in division Reproductive Health of Biology – Class 12

Answer 1

Correct choice is (c) Both countries A and B will have the same population

Explanation: Population fold change  = (Final population / Initial population) / (Time period)

Therefore, the population fold change for country A = (2 billion / 1 billion) / (10 years) = 2X/year

Whereas, the population fold change for country B  = (800 million / 160 million) / (10 years) = 5X/year

Now, population by 2030 = Population at 2020 * Population fold change * Time period between 2030 and 2020

Therefore, the population for country A at 2030 = 2 billion * 2X/year * 10 years = 4 billion

And the population for country B at 2030 = 800 million * 5X/year * 10 year = 4000 million = 4 billion

Hence both countries will have the same population at the end of 2030, after which the population of country B will remain higher than country A.