The average of marks obtained by $100$ candidates in a certain examination is $30 .$ If the average marks of passed candidates is $35$ and that of the failed candidates is $10,$ what is the number of candidates who passed the examination?

The average of $50$ numbers is $38 .$ If two numbers, namely $45$ and $55$ are discarded, the average of the remaining numbers is

In the first $30$ overs of a cricket match, the run rate was $5.2 \,runs/over.$ What is the required run rate in the remaining $20$ overs to reach the target of $280$ runs?

A family consists of grand parents, parents and three grand children. The average age of the grand parents is $67\, years,$ that of the parents is $35\, years$ and that of the grand children is $6 \,years.$ What is the average age of the family? (in $years$)

The daily earnings of a taxi driver during a week are: $Rs.0\,, Rs.65\,, Rs.70\,, Rs.52.50\,, Rs.63\,, Rs.73\,$ and $Rs.68$ What is his average daily earning for the week? (in $Rs.$)

The average of $17$ numbers is $10.9 $ If the average of first nine numbers is $10.5$ and that of the last $9$ numbers is $11.4,$ the middle number is