$19$ persons went to a hotel for a combined dinner party. $13$ of them spent $Rs.\, 79$ each on their dinner and the rest spent $Rs.\, 4$ more than the average expenditure of all the $19 .$ What was the total money spent by them.

Of the three numbers whose average is $60,$ the first is one-fourth of the sum of the others. The first number is

The average of $5$ consecutive integers starting with $m$ is $n$. What is the average of $6$ consecutive integers starting with $( m +2) ?$

The average of $13$ results is $50 .$ If the average of first $7$ results is $52$ and that of last $7$ results is $49,$ find the $7^{th}$ result.

The average age of $20$ boys in the class is $15.6\, years.$ Five new boys join and the new average becomes $15.56\, years.$ What is the average age of the five new boys? (in $years$)

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: