$A$ batsman scores $87$ runs in the $21^{st}$ match of his career. His average runs per match increase by $2.$ What is his average before the $21^{st}$ match?

The average of two numbers is $62$. If $2$ is added to the smaller number,the ratio between the numbers becomes $1:2$. The smaller number is

If the average of $6$ consecutive even numbers is $25,$ the difference between the largest and the smallest number is

The average salary,per head,of all the workers of an institution is $Rs.\, 60$. The average salary of $12$ officers is $Rs.\, 400$; the average salary,per head,of the rest is $Rs.\, 56$. The total number of workers in the institution is:

The average of marks obtained by $100$ candidates in a certain examination is $30$. If the average marks of passed candidates is $35$ and that of the failed candidates is $10$,what is the number of candidates who passed the examination?

The average contribution of $5$ men to a fund is $Rs.\,35.$ $A$ sixth man joins and pays $Rs.\,35$ more than the resultant average of $6$ men. The total contribution of all the six men is (in $Rs.$)