What percent of $4 \text{ km}$ is $8 \text{ meters}$?

If $x$ $\%$ of $y$ is $100$ and $y$ $\%$ of $z$ is $200,$ then find a relation between $x$ and $z$.

In an examination,$37 \frac{1}{2} \%$ of the candidates were girls. If $75 \%$ of the boys and $62 \frac{1}{2} \%$ of the girls passed,and $342$ girls failed,find the number of boys who failed.

$67 \%$ of $801 - 231.17 = ? - 23 \%$ of $789$

$x \%$ of $y + ? \%$ of $x = x \%$ of $(x + y)$

The population of a town is $32000$. It increases $15\%$ annually. What will it be in $2$ years?