Find the sub-duplicate ratio of $81: 64$.

The present ages of Reena and Usha are $24$ and $36$ years,respectively. What was the ratio between the ages of Usha and Reena $8$ years ago?

The sum of three numbers is $124$. If the ratio between the first and second is $2:3$ and that between the second and third is $7:9$,then the third number is

₹ $600$ is divided among $A, B$ and $C$. If $\frac{2}{5}$ of $A$'s share plus ₹ $40$,$\frac{2}{7}$ of $B$'s share plus ₹ $20$,and $\frac{9}{17}$ of $C$'s share plus ₹ $10$ are all equal,then what is $A$'s share in ₹?

The ratio of the number of boys and girls in a college is $7:8$. If the percentage increase in the number of boys and girls is $20\%$ and $10\%$ respectively,what will be the new ratio?

If the income of $A$,$B$,and $C$ is in the ratio of $2: 5: 11$ and the income of $B$ is ₹ $291$ more than that of $A$,then the income of $C$ is (in ₹).