Find the $4^{th}$ proportional to $4, 16$ and $7$.

Three brothers divided ₹ $1620$ among themselves in such a way that the share of the second brother is equal to $\frac{5}{13}$ of the share of the other two combined. What is the share of the second brother?

$A, B, C$ and $D$ purchase a gift worth $Rs. 60$. $A$ pays $\frac{1}{2}$ of what others are paying,$B$ pays $\frac{1}{3}$ of what others are paying,and $C$ pays $\frac{1}{4}$ of what others are paying. What is the amount paid by $D$?

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?

The ratio of incomes of $P$ and $Q$ is $3:4$ and the ratio of their expenditures is $2:3$. If both of them save $Rs. 6000$,the total income of $P$ is (in $Rs.$):

If $A: B = 2: 3$,$B: C = 4: 5$,and $C: D = 6: 7$,then $A: B: C: D$ is