For a rectangle,the length and breadth are increased by $10 \%$ and $20 \%$,respectively. The percentage increase in area is:

An empty fuel tank of a car was filled with $A$ type petrol. When the tank was half-empty,it was filled with $B$ type petrol. Again when the tank was half-empty,it was filled with $A$ type petrol. When the tank was half-empty again,it was filled with $B$-type petrol. What is the percentage of $A$ type petrol at present in the tank?

Ram donated $4 \%$ of his income to a charity and deposited $10 \%$ of the rest in a bank. If now he has $Rs$ $8640$ left with him,then his income is

Two numbers are $90 \%$ and $75 \%$ lesser than a third number. By what percentage should the first number be increased so that it becomes equal to the second number?

In expressing a length $81.472 \, km$ as nearly as possible with three significant digits,find the percentage error?

Two numbers are $50 \%$ and $80 \%$ less than a third number. By what percentage must the second number be increased to make it equal to the first number?