The average of 10 observations is 21. A new observation is included and the average of these 11 numbers is 1 less than the prevoius average. The 11^th observation is____

Average weight of 25 students of a class is 50 kg. If the weight of the class teacher is included, the average is increased by 1 kg. The weight of the teacher 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 weight of 12 parcels is 1.8 kg. Addition of another new parcel reduces the average weight by 50 g. What is the weight of the new parcel?

The average of 11 numbers is 7. If each number is doubled, what will be the new average of the numbers?

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

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:

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: