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 30 numbers is 15. The average of the first 18 numbers is 10 and that of the next 11 numbers is 20. The last number is

Out of 20 boys, 6 are each of 1 m 15 cm height, 8 are of 1 m 10 cm and rest of 1 m 12 cm. The average height of all of them is

Six tables and twelve chairs were bought for ₹ 7,800. If the average price of a table is ₹750, then the average price of a chair would be

if 20% of A = 50% of B, then what percentage of A is B?