The average weight of $25$ persons is increased by $1 \, kg$ when one man weighing $60 \, kg$ is replaced by a new person. What is the weight of the new person (in $kg$)?

The average marks of $40$ students in an examination was $25$. It was later found that the marks of one student had been wrongly entered as $73$ instead of $37$. What is the value of the correct average?

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

The average monthly salary of a staff of $9$ persons is $Rs.\, 2450$. One member of the staff whose monthly salary is $Rs.\, 2650$ is transferred. Find out the average salary of the remaining $8$ persons of the staff (in $Rs.$).

The average of marks obtained by $120$ candidates was $35.$ If the average of marks of passed candidates was $39$ and that of failed candidates was $15,$ the number of candidates who passed the examination is

The average of a batsman after $25$ innings was $56$ runs per innings. If after the $26^{th}$ inning his average increased by $2$ runs,then find his score in the $26^{th}$ inning?