There were $35$ students in a hostel. If the number of students is increased by $7,$ the expenditure on food increase by $Rs. \,42$ per $day$ while the average expenditure of students is reduced by $Rs.\, 1.$ What was the initial expenditure on food per day? (in $Rs.$)

In an examination, out of $20$ students in a class, in Mathematics $2$ students scored $100$ marks $, 3$ students scored $0,$ and average marks for rest of the students was $40 .$ What is the average mark of the whole class ? (in $marks$)

A man spends $Rs.\, 1800$ monthly on an average for the first four months and $Rs. \,2000$ monthly for the next eight months and saves $Rs. \,5600$ a year. His average monthly income is (in $Rs.\,$)

A cricketer has a certain average for $10$ innings. In the eleventh inning, he scored $108$ runs, thereby increasing his average by $6$ runs. His new average is

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