$A$ 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?

₹ $1980$ is divided among $A, B$ and $C$ such that half of $A$'s part,one-third of $B$'s part,and one-sixth of $C$'s part are equal. Then $B$'s part is (in ₹):

One year ago,the ratio between Ram's and Shyam's salaries was $3:5$. The ratios of their individual salaries of last year to the present year are $2:3$ and $4:5$ respectively. If their total salary for the present year is $Rs. 8600$,find the present salary of Ram (in $Rs.$)?

The ratio of wine and water in a drum is $3:1$. What part of the mixture is taken out and replaced with an equal amount of water so that the ratio of wine and water in the mixture becomes $1:1$?

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?

Sachin is younger than Rahul by $4$ years. If their ages are in the respective ratio of $7:9$,how old (in years) is Sachin?