The average age of four members of a family is $32$ years. If the age of a guest is included,then the average age increases by $12.5 \%$. What is the age (in years) of the guest?

Out of $9$ persons,$8$ persons spent $Rs. 30$ each for their meals. The ninth one spent $Rs. 20$ more than the average expenditure of all the nine. The total money spent by all of them was (in $Rs.$)

The average age of $20$ boys in the class is $15.6$ years. Five new boys join and the new average becomes $15.56$ years. What is the average age of the five new boys (in years)?

The average age of $11$ players of a cricket team is increased by $2 \, \text{months}$ when two of them aged $18 \, \text{years}$ and $20 \, \text{years}$ are replaced by two new players. The average age of the new players is?

Five years ago,the average age of $P$ and $Q$ was $15 \text{ years}$. Now,the average age of $P$,$Q$,and $R$ is $20 \text{ years}$. What will be the age of $R$ after $10 \text{ years}$?

The average of marks of $28$ students in Mathematics was $50$. $8$ students left the school,then this average increased by $5$. What is the average of marks obtained by the students who left the school?