Average - General Questions

The average of 7 numbers is 39. When one more number is added, the average becomes 40. What is the new number?

The average of 20 numbers is 33. When one more number is added, the average becomes 35. What is the new number?

The average weight of 5 persons increases by 2.5 kg when a new person replaces one of them weighing 55 kg. What is the weight of the new person?

What is the average of the first 13 odd numbers?

The average of 20 numbers is 29. When one more number is added, the average becomes 31. What is the new number?