The average age of a husband and wife, who were married $7 \,years$ ago, was $25\, years$ at the time of their marriage, Now, the average age of the family, including husband, wife and a child, born during the interval, is $22\, years.$ What is the present age of the child in $year$ ?

Average weight of $3 \,cm$ men $A , B , C$ is $84 \,kg$. Another man $D$ joins the group and the average now becomes $80 \,kg$. If another man $E$ whose weight is $3 \,kg$ more than that of $D$ replaces $A$ then the averageweight of $B , C , D$ and $E$ becomes $79\, kg .$ The weight of $A$ in $kg$ is

After replacing an old member by a new member, it was found that the average age of five members of a club is the same assit was $3 \,year$ ago. The difference between the ages of the replaced and the new member is ? (in $year$)

David obtained $76,65,82,67$ and $85 \,marks$ (out of $100$ ) in English, Mathematics, Physics, Chemistry and Biology. What is his average $marks$ ?

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 $kg$)?