The arithmetic mean of the scores of a group of students in a test was $52$. The brightest $20\%$ of them secured a mean score of $80$ and the dullest $25\%$ a mean score of $31$. The mean score of the remaining $55\%$ is

The average age of mother,father,and son was $42$ years at the time of the son's marriage. After one year,an infant was born in the family,and after $6$ years of marriage,the average age of the family is $36$ years. What was the age of the bride at the time of marriage in years?

The average salary of $20$ workers in an office is $Rs. 1900$ per month. If the manager's salary is added,the average becomes $Rs. 2000$ per month. The manager's annual salary (in $Rs.$) is

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 odd numbers up to $100$ is?

There was one mess for $30$ boarders in a certain hostel. On the number of boarders being increased by $10,$ the expenses of the mess were increased by $Rs.\, 40$ per month while the average expenditure per head diminished by $Rs.\, 2.$ Find out the actual monthly expenses (in $Rs.$).