How much pure alcohol has to be added to $400 \text{ ml}$ of a solution containing $15 \%$ alcohol to change the concentration of alcohol in the mixture to $32 \%$?

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

In a class of $80$ students and $5$ teachers,each student received sweets equal to $15 \%$ of the total number of students,and each teacher received sweets equal to $25 \%$ of the total number of students. How many sweets were there in total?

From the salary of an officer,$10 \%$ is deducted as house rent,$20 \%$ of the rest,he spends on conveyance,$20 \%$ of the rest he pays as income tax and $10 \%$ of the balance,he spends on clothes. If he is left with ₹ $15552$,find his total salary.

What is $15$ percent of Rs. $34$?

In an examination,a candidate obtains $25\%$ marks and fails by $45$ marks,while another candidate obtains $46\%$ marks and passes by $15$ marks. What are the passing marks?