In a family, the average age of a father and a mother is $35\, years.$ The average age of the father, mother and their only son is $27\, years.$ What is the age of the son ? (in $years$)

A class has $20$ boys and $30$ girls. The average age of boys is $11\, years $ and that of girls is $12\,years.$ What is the average age of the whole class in $year$

A batsman makes a score of $8$ runs in the $16^{\text {th }}$ match and thus increases his average runs per match by $3 .$ What is his average after the $16^{\text {th }}$ match?

The average of runs of a cricket player of $10$ innings was $32 .$ How many runs must he make in his next innings so as to increase his average of runs by $4 \,?$ 

Find the average of all the numbers between $6$ and $34$ which are divisible by $5$

The average monthly expenditure of a family for the first four months is $Rs.\,2750$ for the next three months is $Rs.\,2940$ and for the last five months is $Rs.\,3130.$ If the family saves $Rs.\,5330$ throughout year, find the average monthly income of the family for that year. (in $Rs.$)