Question

The rise in population of a country varies directly with each passing year.
The population has risen by 2 million in past 5 years. Calculate the population rise in next 10 years?

• A. 4 million
• B. 5 million
• C. 6 million
• D. 7 million

Answer 1

The correct option is A 4 million

Let rise in population is represented by $P$ and passing year is represented by $Y$.
Given rise in population varies directly with each passing year.
So, $P\propto Y$
$\Rightarrow \frac{P}{Y}=k$
According to question,
Population has risen by 2 million in past 5 years
$\Rightarrow \frac{P}{Y}=\frac{2}{5}$

We have to find the population rise in next 10 years,
So, $Y=10$ years

$\frac{P}{Y}=\frac{2}{5}$
$\frac{P}{10}=\frac{2}{5}$
$\Rightarrow P=\frac{2}{5}\times 10=4\text{million}$
Hence, the population will rise by 4 milllion in next 10 years.