The average age of Sachin and Ganguli is $35 \,years.$ If Kaif replaces Sachin, the average age becomes $32 \,years$ and if Kaif replaces Ganguli, then the average age becomes $38 \,years.$ If the average age of Dhoni and Irfan be half of the average age of Sachin, Ganguli and Kaif, then the average age of all the five people is:

The average price of $80$ computers in an electronic shop is $Rs.\, 30,000 .$ If the highest and lowest price computers are sold out then the average price of the remaining $78$ computers is $Rs.\, 29,500 .$ The cost of the highest price computer is $Rs.\, 80,000 .$ The cost of lowest price computer is in $Rs.$ 

The average weight of $4$ men $A, B, C$ and $D,$ is $67\, kg.$ The $5^{th}$ man $E$ is included and the average weight decreases by $2 \,kg$. A is replaced by $F.$ The weight of $F$ is $4 \,kg$ more than $E$. Average weight deereases because of the replacement of $A$ and now the average weight is $64\, kg.$ Find the weight of $A ?$

A student finds the average of $10,2$ digit numbers. If the digits of one of the number is interchanged, the average increases by $3.6 .$ The difference between the digits of the $2 -$digit numbers is

What is the average of the squares of the first $19$ natural numbers ?