Question

From year 1980 to 1985 $10\%$ people migrated , and from year 1980 to 1990 $20\%$, then from 1985 to 1990 how many migrated

Answer 1

Let the population in 1980 = x
In 1985, $10\%$ people migrated
Population in 1986 $=x-\frac{10x}{100}=0.9x$
From 1980 to 1990, $20\%$ people migrated
$\Rightarrow$ Population in 1990 $x-\frac{20x}{100}=0.8x$
$\Rightarrow$ Population migration from 1985 to 1990 = 0.9x - 0.8x = 0.1x
$\%migration=\frac{migrationbetween1985to1990}{populationin1985}\times 100=\frac{0.1x}{0.9x}\times 100=\frac{100}{9}=11.111\%$