$A$ milkman makes $20\%$ profit by selling milk mixed with water at $Rs. 9$ per litre. If the cost price of $1 \text{ L}$ pure milk is $Rs. 10$,then the ratio of milk and water in the given mixture is:

The ratio of the number of boys and girls in a school is $3:2$. If $20\%$ of the boys and $25\%$ of the girls are scholarship holders,what percentage of the students does not get the scholarship?

If $A$ and $B$ are in the ratio $3: 4$ and $B$ and $C$ are in the ratio $12: 13$,then $A$ and $C$ will be in the ratio:

$A$'s income is ₹ $140$ more than $B$'s income and $C$'s income is ₹ $80$ more than $D$'s. If the ratio of $A$'s and $C$'s incomes is $2:3$ and the ratio of $B$'s and $D$'s incomes is $1:2$,then the incomes of $A, B, C$ and $D$ are respectively (in ₹):

Four years ago,the father's age was three times the age of his son. The total of the ages of the father and the son after four years will be $64$ years. What is the father's age at present (in years)?

$x$ varies inversely as the square of $y$. Given that $y=2$ when $x=1$. The value of $x$ when $y=6$ will be equal to: