In a mixture of $60 \, \text{litres}$,the ratio of milk and water is $2:1$. What amount of water (in $\text{litres}$) must be added to make the ratio of milk and water $1:2$?

$A$ year ago,the cost of Maruti and Figo were in the ratio of $3:4$. The ratio of present and past year costs of Maruti and Figo are $5:4$ and $3:2$,respectively. If the sum of their present costs is $7.8$ lacs,find the cost (in lacs) of Figo a year ago.

The mean proportional of $0.25$ and $0.04$ is

Ram got twice as many marks in English as in Science. His total marks in English,Science,and Mathematics are $180$. If the ratio of his marks in English and Mathematics is $2:3$,what are his marks in Science?

If an alloy contains copper and silver in the ratio $3:7$,then the percentage quantity of silver in the alloy is

$A$ person distributes his pens among four friends $A, B, C$ and $D$ in the ratio $\frac{1}{3}: \frac{1}{4}: \frac{1}{5}: \frac{1}{6}$. What is the minimum number of pens that the person should have?