Question

The population of a town is 32400. For the past 2 years the population has been decreasing at the rate of 10% per annum due to people migration to other cities. What was the population 2 years ago.

Answer 1

Dear Student,

Let the population of town 2 years ago is x
at the end of 1 year population
$x-\frac{10}{100}\times x\Rightarrow \frac{90x}{100}$
Similarly, at the end of 2 nd year population will be $\frac{90}{100}\times \frac{90x}{100}$
but it is given that at the end of 2 years the population of town = 32400
therefore,
$$\begin{gathered} \frac{90}{100}\times \frac{90x}{100}=32400 \\ x=\frac{32400\times 100\times 100}{90\times 90} \\ x=40,000 \end{gathered}$$

Regards