A bag contains $₹ 140$ in the form of $50 \text{paise}$ $₹ 1 \text{and} ₹ 2$  coins in the ratio of  $6:3:7$. Find the total number of coins.

If the compounded ratio of $\sqrt{2}:1,3:\sqrt{5} and \sqrt{20}:9$ is $a\sqrt{a}:b$, then find the value of $a+b$.

Find the duplicate ratio of $5\sqrt{7}:7\sqrt{5}$.

If the triplicate ratio of $1:3xy$is $1:k{x}^3{y}^3$, find the value of $k$.

Find the sub duplicate of $9x^2:49y^2$.