The average weight of five persons sitting in a boat is $38\, kg.$ The average weight of the boat and the persons sitting in the boat is $52\, kg.$ What is the weight of the boat (in $kg$)?

Three year ago, the average age of a family of five members was $27 \,year.$ The present average age is also $27 \,year$ after the inclusion of a child into the family. Find the age of the child in $year$ ?

A batsman score $98$ runs in the $17^{\text {th }}$ match of his career. His average runs per match increase by $2.5$ What is his average before the $17^{\text {th }}$ match?

The average salary per head of all workers of an institution is $Rs. \,60\,.$ The average salary per head of $12$ officers is $Rs. \,400 .$ The average salary per head of the rest is $Rs.$ $56 .$ Then, the total number of workers in the institution is?

The average expenditure of a man for the first five months is $Rs.\, 3600$ and for next seven months it is $Rs.\, 3900 .$ If he saves $Rs.\, 8700$ during the $year,$ his average income per $month$ is (in $Rs.$)