The average age of $5$ members is $21 \,years.$ If the age of the youngest member be $5 \,years,$ find out the average age of the family at the birth of the youngest member.(in $years$)

A batsman has a certain average of runs for $12$ innings. In the $13^{th}$ innings, he scores $96$ runs and thereby increasing his average by $5$ runs. What is his average after the $13^{th}$ innings ?

The average marks of $120$ students are $35.$ If average of passed students was $39$ and failed students was $15,$ then Find the number of students who have passed?

If the mean of $5$ observation $x, x+2, x+4, x+6$ and $x+8$ is $11,$ then the mean of the last three observations is

The average monthly income of $P$ and $Q$ is $Rs.\,5050.$ The average monthly income of $Q$ and $R$ is $Rs.\,6250$ and the average monthly income of $P$ and $R$ is $Rs.\,5200.$ The monthly income of $P$ 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 $4 \,?$