The average of 30 numbers is 40 and that of the other 40 numbers is 30. The average of all the numbers is-

There are two groups A and B of a class, consisting of 42 and 28 students respectively. If the average weight of group A is 25 kg and that of group B is 40 kg, find the average weight of the whole class. 

The average of twenty-five numbers is 54. The average of the first 13 numbers and that of the last 13 numbers is 52.8 and 62.2, respectively. If the 13th number is excluded, then what is the average of the remaining numbers (correct to one decimal place)?

The average mathematics marks of two Sections A and B of class IX 131 the annual examination is 74. The average marks of Section A is 77.5 and that of Section B is 70. The ratios of the number of students of Section A and B is:

 In a family, the average age of a father and a mother is 35 years. The average age of the father, mother and their only son is 27 years. What is the age of the son? 

The average age of a husband and wife, who were married 4 years ago, was 25 years at the time of their marriage. The average age of the family consisting of husband, wife and a child, born during the interval is 20 years today. The age of the child is:

Find the average of 1.11, 0.01, 0.101, 0.001, 0.11

The average age of a husband and his wife was 27 years when the child was born, the average age of the husband, the wife and new-born child is 21 years now. The present age of the child is: