The average weight of three boys $A, B$ and $C$ is $54 \frac{1}{3} \,kg,$ while the average weight of three boys $B , D$ and $E$ is $53 \,kg .$ What is the average weight of $A , B , C , D$ and $E$ ?(in $kg$)

The mean of $50$ observations was $36 .$ It was found later that an observation $48$ was wrongly taken as $23 .$ The corrected new mean is

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

The average salary of the entire staff in a office is $Rs.\, 120$ per $month.$ The average salary of officers is $Rs.\, 460$ and that of non-officers is $Rs. \,$ $110 .$ If the number of officers is $15,$ then find the number of non-officers in the office ?

The average age of a man and his two twin born on the same day is $30 \,year.$ The ratio of the ages of father and one son is $5: 2,$ what is the father's age in $year?$