Question

The population of a city is 2,20,000. If the population decreases by 10% every year, what will be the population after 2 years?
[3 Marks]

Answer 1

Given,
Present population of the city, P = 2,20,000
Rate at which it is decreasing, R = 10 p.c.p.a.

So, population after 2 years i.e., A can be written as:

$=P(1+\frac{r}{100}{)}^n$
[1 Mark]

$=2,20,000(1+\frac{-10}{100}{)}^2$

$=2,20,000(\frac{90}{100}{)}^2$

$=2,20,000\times \frac{90}{100}\times \frac{90}{100}$

$=1,78,200$
[1.5 Marks]

So, the population of the city after 3 years will be equal to 1,78,200.
[0.5 Marks]