$15 \%$ of $578 + 22.5 \%$ of $644 = ?$

In measuring the sides of a rectangle,one side is taken $10 \%$ in excess and the other $20 \%$ in deficit. Find the error per cent in area calculated from the measurement.

In an examination,$35 \%$ of the students passed and $455$ failed. How many students appeared for the examination?

Two numbers $A$ and $B$ are such that the sum of $6\%$ of $A$ and $4\%$ of $B$ is two-thirds of the sum of $6\%$ of $A$ and $8\%$ of $B$. Find the ratio of $A:B$.

If $A$ is $20 \%$ more than $360,$ then what is the value of $A$?

The difference between a discount of $35 \%$ and two successive discounts of $20 \%$ and $20 \%$ on a certain bill was ₹ $22$. Find the amount of the bill.