NIFT PG 2020 Question Paper with solutions

Let the population in the year $1980=\mathit{x}$
Then, the population in the year $1990=120\%$ of $\mathit{x}$
Then, the population in the year 2000
$=120\%$ of $120\%$ of $\mathit{x}$
And the population in the year 2010
$=120\%$ of $120\%$ of $120\%$ of $\mathit{x}$
$=\frac{120}{100}\times \frac{120}{100}\times \frac{120}{100}\times \mathit{x}$
$=\frac{6}{5}\times \frac{6}{5}\times \frac{6}{5}\times \mathit{x}=\frac{216}{125}\mathit{x}$
Hence, required percentage
$=\frac{\frac{216\mathit{x}}{125}-\mathit{x}}{\mathit{x}}\times 100\%$
$=\frac{91}{125}\times 100\%=72.8\%$