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

In a college,$150$ students of $MBA$ are enrolled. The ratio of boys to girls is $7:8$. There are three disciplines in the college: Marketing,$HR$,and Finance. In the Marketing discipline,there are $50\%$ of the total girls and $40\%$ of the total boys. In the $HR$ discipline,there are $30\%$ of the total girls and $30\%$ of the total boys. In the Finance discipline,there are $20\%$ of the total girls and $30\%$ of the total boys. $7$ boys and $9$ girls are in both $HR$ and Marketing. $6$ boys and $7$ girls are in both $HR$ and Finance. $5$ boys and $8$ girls are in both Marketing and Finance. $2$ boys and $3$ girls are enrolled in all three disciplines. What is the ratio of boys to girls only in the Marketing discipline?

The ratio of two numbers is $4:5$. If both numbers are increased by $4$,the ratio becomes $5:6$. What is the sum of the two numbers?

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

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 $1:2$?

$Rs. 366$ are divided among $A, B$ and $C$ such that $A$ gets $\frac{1}{2}$ as much as $B$ and $C$ together,and $B$ gets $\frac{2}{3}$ as much as $A$ and $C$ together. What is the share of $A$ (in $Rs.$)?