The average of the two-digit numbers, which remain the same when the digits interchange their position is

The average of $11$ numbers is $10.9$ If the average of the first six is $10.5$ and the average of last six is $11.4,$ find the middle (sixth) number.

In an examination the average marks was found to be $60.$ The marks of $80$ candidates had to be changed from $95$ to $70$ each and the average came down to $55$ marks. The total number of candidates attended the examination were

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 $years$)

Ten years ago the average age of $P$ and $Q$ was $20\, years.$ Average age of $P, Q$ and $R$ is $30\, years$ now. After $10 \,years,$ the age of $R$ will be (in $years$)

The average of three numbers is $135 .$ The largest number is $195$ and the diference between the other two is $20 .$ The smallest number is