Depreciation applicable to an equipment is $20 \%$. The value of the equipment $3$ years from now will be less by: (in $\%$)

$A$ person scores $45 \%$ of the total marks in the exam and still fails by $40$ marks. The passing percentage of the exam is $55 \%$. What is the maximum marks of the exam?

$A$ salesman is allowed $5 \frac{1}{2} \%$ discount on the total sales made by him plus a bonus of $\frac{1}{2} \%$ on the sales made over $₹ 10000$. If his total earnings are $₹ 1990$,find the total sales.

Milk contains $5 \%$ water. What quantity of pure milk should be added to $10$ litres of milk to reduce this to $2 \%$?

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

In an examination,the percentage of students qualified to the number of students appeared from school $A$ is $70 \%$. In school $B$,the number of students appeared is $20 \%$ more than the students appeared from school $A$ and the number of students qualified from school $B$ is $50 \%$ more than the students qualified from school $A$. What is the percentage of students qualified to the number of students appeared from school $B$?