The population of a town increases by $8\%$ annually. If the present population is $54000$, what was it a year ago?

The value of a machine depreciates every year by $20\%$. If the present value of the machine be $₹160000$, what was its value last year?

An alloy contains $40\%$ copper, $32\%$ nickel and rest zinc. Find the mass of zinc in one kg of the alloy.

Balanced diet should contain $12\%$ of proteins, $25\%$ of fats and $63\%$ of carbohydrates. If a child needs $2600$ calories in his food daily, find in calories the amount of each of these in his daily food intake.

Gunpowder contains $75\%$ nitre and $10\%$ sulphur. Find the amount of gunpowder which carries $9 \mathrm{kg}$ nitre. What amount of gunpowder would contain $2.5 \mathrm{kg}$ sulphur?

Divide $₹7000$ among $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}$ such that $\mathrm{A}$ gets $50\%$ of what $\mathrm{B}$ gets and $\mathrm{B}$ gets $50\%$ of what $\mathrm{C}$ gets.

Find the percentage of pure gold in $22$-carat gold, if $24$-carat gold is $100\%$ pure.

The salary of an officer is increased by $25\%$. By what percent should the new salary be decreased to restore the original salary?