The average of the squares of of first ten natural numbers is
$35.5$
$36$
$37.5$
$38.5$
After replacing an old member by a new member, it was found that the average age of five members of a club is the same assit was $3 \,year$ ago. The difference between the ages of the replaced and the new member is ? (in $year$)
The average temperature of Monday, Tuesday, Wednesday and Thursday is $60^{\circ}$. The average temperature for Tuesday, Wednesday, Thursday and Friday is $63^{\circ}$. If the ratio of temperature for Monday and Friday is $21: 25,$ then what is the temperature of Friday? (in $^{\circ}$)
Last year, $5$ companies had an average of $16$ non working days each, and $2$ companies had $5$ fewer non working days each. What was the average number of non working days given by the same companies this $year$ ?
The average weight of $5$ persons, sitting in a boat, is $38 \,Kg$. If the average weight of the boat and the persons sitting in the boat is $52 \,Kg$, what is the weight of the boat? (in $kg$)
$12 \%$ of Kaushal's monthly salary is equal to $16 \%$ of Nandini's monthly salary. Suresh's monthly salary is half that of Nandini's monthly salary. If Suresh's annual salary is $Rs.\,1.08$ $lacs.$ What is Kaushal's monthly salary? (in $Rs.$)