The average weight of $15$ oarsmen in a boat is increased by $1.6\, kg$ when one of the crew, who weighs $42\, kg$ is replaced by a new man. Find the weight of the new man (in $kg$)

The average age of $80$ boys in a class is $15.$ The average age of a group of $15$ boys in the class is $16$ and the average age of another $25$ boys in the class is $14 .$ What is the average age of the remaining boys in the class ?

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.

Out of three numbers, the first is twice the second and is half of the third. If the average of the three numbers is $56,$ the three numbers in order are

The average age of $10$ men is increased by $2 \,years$ when one of them of $25 \, years$ age, is replaced by new man. What is the age of new man? (in $years$)

The average of the boys in a class is $16\, years$ and that of girls is $15\, years.$ The average age for the whole class is