The average income of $A$ for $15$ days is $Rs. 70$. The average for the first five days is $Rs. 60$ and that for the last nine days is $Rs. 80$. $A$'s income for the sixth day is (in $Rs.$):

The average age of $30$ girls is $13$ years. The average age of the first $18$ girls is $15$ years. Find the average age of the remaining $12$ girls.

The average annual income (in $Rs.$) of certain agricultural workers is $S$ and that of other workers is $T$. The number of agricultural workers is $11$ times that of other workers. Then the average annual income (in $Rs.$) of all the workers is

The average of the first nine prime numbers is:

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

There are $35$ students in a hostel. If the number of students increased by $7$,the expenses of the mess were increased by $Rs. 42$ per day while the average expenditure per head decreased by $Rs. 1$. Find out the actual expenditure of the mess (in $Rs.$).