How to find Average

How is average speed obtained ?

The average of x numbers is y^(2) and the average of y numbers is x^(2) . Find the average of all the numbers taken together

The average expenditure of 4 Boys and 3 Girls is Rs. 120 . If the average expenditure of Boy's is Rs. 150 then find out average expenditure of Girl's.

The average weight of 55 students is 55 kg , and the average weight of another 45 students is 45 kg . Find the average weight of all the students .

If the average marks of 30 students of section A is 55 and the average marks of 30 students of section B is 60 ,then find the combined average of both the sections.