Question

A country's birth rate is the number of births per year per $1000$ people in the country, and a country's death rate is the number of deaths per year per $1000$ people. Immigration refers to the number of people who move into a country each year, and emigration refers to the number of people who move out of the country each year. A country's population growth is determined by these four variables. Table $1$ gives birth, death, immigration and emigration rates in four countries and lines $1-4$ in Figure $1$ model in the population for the four countries shown over time.

	Birth	Death	Immigration	Emigration
East Zealand	$20$	$x$	$1000$	$1000$
West Zealand	$21$	$21$	$12100$	$y$
South Zealand	$36$	$24$	$z$	$500$
North Zealand	$13$	$13$	$82000$	$9600$

Name the country whose population is represented by line $1$.

• A. East Zealand
• B. West Zealand
• C. North Zealand
• D. South Zealand

Answer 1

Answer: (D)

South Zealand

$\Rightarrow$ Line $1$ shows exponential growth, because the line curves upward.

$\Rightarrow$ Since, birth rate and death rate are per $1,000$ people, a birth rate higher than a death rate will result in exponential growth (because births-deaths will increase as the population increases).

$\Rightarrow$ Immigration and emigration numbers are per year and therefore have a linear effect on the graph (as the absolute change in the population due to immigration-emigration is constant).

$\Rightarrow$ South Zealand has more births per $1,000$ than deaths per $1,000$.

$\therefore$ Correct answer is option $D$ South Zealand.