The average earning of a mechanic for the first four days of a week is $Rs.\,18$ and for the last four days is $Rs.\,22.$ If he earns $Rs.\, 20$ on the fourth day, his average earning for the whole week is (in $Rs.$)

The average weight of all the $11$ players of Indian cricket team is $50\, kg.$ If the average of first six lightest weight players is $49\, kg$ and that of the six heaviest players is $52\, kg$. The average weight of the player which lies in the sixth position in the list of players when all the $11$ $players$ are arranged in the order of $increasing$ or $decreasing$ $weights$ (in $kg$)

Out of four numbers, whose average is $60,$ the first one is one-fourth of the sum of the last three. The first number 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 $Rs.$)

In a set of prime and composite numbers, the composite numbers are twice the number of prime number and the average of all the numbers of the set is $9 .$ If the number of prime numbers and composite numbers are exchanged then the average of the set of numbers is increased by $2 .$ If during the exchange of the numbers the average of the prime numbers and composite numbers individually remained constant, then the ratio of the average of composite numbers to the average of prime numbers (initially) was