The average temperature for Monday, Tuesday, Wednesday and Thursday was $48^{\circ}$. The average temperature for Tuesday, Wednesday, Thursday and Friday was $52^{\circ} .$ If the temperature on Monday was $42^{\circ} .$ then the temperature on Friday was (in $degrees$)

In a coconut grove, $(x+2)$ trees yield $60$ $nuts$ per $year,$ $x$ trees yield $120\, nuts$ per $ year,$ and $(x-2)$ trees yield $180 \,nuts$ per $year$. If the average yield per $year$ per tree be $100,$ find the value of $x .$

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 $year$ ?

Out of four numbers the average of the first three is $16$ and that of the last three is $15 .$ If the last number is $20$ then the first number is

If the mean of $a, b, c$ is $M$ and $a b+b c+c a=0,$ then the mean of $a^{2}, b^{2}, c^{2}$ is

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