An aeroplane flies along the four sides of a square field at speeds of $200, 400, 600$ and $800 \, km/hr$. The average speed of the plane in the flight around the field in $km/hr$ is:

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:

$A$ student finds the average of $10$ two-digit numbers. If the digits of one of the numbers are interchanged,the average increases by $3.6$. The difference between the digits of that two-digit number is:

The sum of eight consecutive numbers of Set $A$ is $376$. What is the sum of $5$ consecutive numbers of another set if its minimum number is $15$ ahead of the average of Set $A$?

The average age of three boys is $15$ years. If the ratio of their ages is $3:5:7$,what is the age of the oldest boy in years?

The average of three consecutive odd numbers is $52$ more than $\frac{1}{3}$ of the largest of these numbers. What is the smallest of these numbers?