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 $year$)

The average marks of a class of $35$ children is $35 .$ The marks of one of the students, who got $35,$ was incorrectly entered as $65 .$ What is the correct average of the class?

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 $Rs.$)

Average age of $A, B$ and $C$ is $84\, years.$ When $D$ joins them the average age becomes $80\, years.$ A new person, $E,$ whose age is $4 \,years$ more than $D,$ replaces $A$ and the average of $B, C, D$ and $E$ becomes $78\, years.$ What is the age of $A$ ? (in $years$)

The average of marks obtained by $120$ candidates was $35.$ If the average of marks of passed candidates was $39$ and that of failed candidates was $15,$ the number of candidates who passed the examination is

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 $4 \,?$