Question

In $2005$, for each of the $14$ million people present in a country, $0.028$ were born and $0.008$ died during the year. Using exponential equation, the number of people present in $2015$ is predicted as

• A. $25$ millions
• B. $17$ millions
• C. $20$ millions
• D. $18$ millions

Answer 1

Answer: (B)

Exponential equation gives population growth rate as
$\frac{dN}{dt}=rN$
Here, $r=$ intrinsic rate of natural increase
$N=$ size of original population
$\frac{dN}{dt}=$ Increase in population size per unit time ($1$ year in this case)
$r$ is the difference between birth and death rate.
$r=0.028-0.008=0.02$
$\therefore \frac{dN}{dt}=0.02\times 14$ million $=0.28$ million
Over $10$ years $(2005-2015)$, this number will become
$=2.8$ million.
Expected population in $2015=(14+2.8)$ million
$=17$ million (approx.)