David obtained $76,65,82,67$ and $85 \,marks$ (out of $100$ ) in English, Mathematics, Physics, Chemistry and Biology. What is his average $marks$ ?

The average age of mother, father and son was $42\, years.$ at the time of the marriage of the son. After one year an infant was born in the family and after $6\, years$ of marriage the average age of the family is $36\, years.$ What was the age of the bride at the time of marriage in $year.$

A batsman, in his $12^{th}$ innings, makes a score of $63$ runs and thereby increases his average score by $2.$ The average of his score after $12^{th}$ innings is

There was one mess for $30$ boarders in a certain hostel. On the number of boarders being increased by $10,$ the expenses of the mess were increased by $Rs.\,40$ per month while the average expenditure per head diminished by $Rs.\,2.$ Find out actual monthly expenses. (in $Rs.$)

On $24^{\text {th }}$ May, 2008 the maximum temperature of Delhi, Kollkata and Mumbai were recorded as $35^{\circ} C$, $33^{\circ}$ and $34^{\circ} C$ respectively. What was the maximum temperature of Chennai so that the average maximum temperature of those cities would be $35^{\circ} C$ (in $^{\circ} C$ )

In a school with $600$ students, the average age of the boys is $12$ $years$ and that of the girls is $11\, years.$ If the average age of the school is $11 \,years$ and $9 \,months,$ then the number of girls in the school is