The average weight of 8 persons increases by 2.5 kg when a new person comes in place of one of them weighing 65 kg. What might be the weight of the new person?

The average height of 25 boys is 1.4 m. When 5 boys leave the group, then the average height increase by 0.15 m. What is the average height of the 5 boys who leave ?

When a commodity is sold for Rs. 34.80, there is a loss of 2%. What is the cost price of the commodity?

David got two and a half times as many marks in English as in History. If his total marks in the two subjects are 140, the marks obtained by him in English are: