In Java :

Exercise 29: Write a program that prints out the first 20 squares (1, 4, 9, 16,..., 400), one per line. Use a for loop.

Exercise 30: Modify your answer to Exercise 29 so that it prints the sum of the first 20 squares (1 + 4 + 9 + 16 + ... + 400).

Exercise 31: Modify your answer to Exercise 30 so that it finds and displays the average of the first 20 squares.