The average marks of $40$ students in an English exam is $72$. Later,it is found that three marks $64, 62,$ and $84$ were wrongly entered as $68, 65,$ and $73$. The average after the mistakes were rectified is:

$A, B, C$ and $D$ are four consecutive even numbers,respectively,and their average is $65$. What is the product of $A$ and $D$?

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

If the mean of $a, b, c$ is $M$ and $ab + bc + ca = 0$,then the mean of $a^2, b^2, c^2$ is

The average of a non-zero number and its square is $5$ times the number. The number is

The cost of $5 \,kg$ of apples is $Rs. \, 450$. The cost of $12$ dozen mangoes is $Rs. \, 4320$,and the cost of $4 \,kg$ of oranges is $Rs. \, 240$. What is the total cost of $8 \,kg$ of apples,$8$ dozen mangoes,and $8 \,kg$ of oranges? (in $Rs.$)