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

The quantity of water needed to reduce $9 \ ml$ of shaving lotion containing $50 \%$ alcohol to a lotion containing $30 \%$ alcohol is: (in $ml$)

The population of Delhi increases by $10 \%$ every year. If the current population of Delhi is $1,331,000$,what was its population $3$ years ago?

The length of a rectangle is increased by $30 \%$ and the breadth by $20 \%$. Then the perimeter of the rectangle will increase by what percent?

What fraction is $0.6 \%$?

The population of a town increases by $2.5 \%$ annually but decreases by $0.5 \%$ every year due to migration. What will be the net percentage increase in population after $2$ years (in $\%$)?