The mean of the cubes of the fist n natural number is

Prove, by Principle of Mathematical Induction, that the sum of the cubes of three consecutive natural numbers is divisible by 9.

Find the mean and variance of the first n natural numbers.

The mean of first 10 natural numbers is

Find the sum of of the products of first n natural numbers, taken two at a time .

Find the sum of first n natural numbers.

The arithmetic mean of first n odd natural numbers is :

Statement 1 The difference between the sum of the first 100 even natural numbers and the sum of the first 100 odd natural numbers is 100. Statement 2 The difference between the sum opf the first n even natural numbers and sum of the first n odd natural numbers is n.