If $34\%$ of a number is $85$, find the number.

The value of a machine depreciates every year by $10\%$. It was purchased one year ago. If the present value of the machine is $₹54000$, what was its value last year?

An alloy contains $30\%$ copper, $42\%$ nickel and rest zinc. Find the mass of zinc in $1 \mathrm{kg}$ of alloy.

In a class, $60\%$ of the total number of students are boys and there are $14$ girls. How many students are there in the class?

Which is largest in $8\frac{1}{3}\%, \frac{4}{25}$ and $0.15$?