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

$10\, kg$ of rice priced at $Rs. \,12$ per $kg$ is mixed with $6\, kg$ of rice priced at $Rs. \,16$ per $kg$. Find the average price in $Rs.$ per $kg$ of the whole mixture?

The average age of $6$ members of a family is $20\, years.$ If the age of a servant is included, the average age increased by $25 \%$. What is the age (in $years$) of the servant ?

A club has $15$ men and $25$ women. The average age of men is $10\, years$ and the average age of women is $12 \,year.$ What is the average age of the whole club in $year$?

The sum of the ages of father and son at present is $33\,years.$ Two years ago the product of their ages was $28 \,years.$ What is the age of the father and the son? (in $years$)

A motorist covered the first $20\, km$ of his journey in 30 mifitutes and the remaining $29\, km$ in $40\, minutes$. His average speed in $km / hr$ is: