Three $years$ ago the average age of a family of $5$ members was $17\, years.$ With the birth of a new baby, the average remains the same three even today. Find out the age of the baby.(in $years$)

The average weight of $100$ students is $32\, kg$. The average weight of first $49$ students is $30\, kg$ and that of last $50$ students is $34\, kg$. What is the weight (in $kg$ ) of the $50^{ th }$ student ?

The average marks of students in an examination was $65 .$ It was later found that the marks of one students had been wrongly entered as $83$ instead of $38.$ the correct average is ?

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 $year$ ?

The average age of Donald, his wife and their two children is $23\, years.$ His wife is just $4 \,year$ younger than Donald himself andxhis wife was $24\, years$ old when his daughter was born. He was $32 \,years$ old when his son was born. Th average age of Donald and his daughter is ? (in $year$)

Amitabh's average expenditure for the $January$ to $June$ is $Rs.\, 4200$ and he spends $Rs.\, 1200$ in $January$ and $Rs. \,1500$ in $July.$ The average expenditure for the month of $February$ to $July$ is (in $Rs.$)