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

Find the sum of all possible products of the first n natural numbers taken two by two.

Find the sum of first n natural numbers.

Find the sum of first 100 natural numbers.

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

The sum of first 30 natural numbers is:

Find the mean of first five natural numbers.

Find a cubic polynomial with the sum, sum of the product of its zeroes taken two at a time, and the product of its zeroes as 2, - 7, - 14 respectively.

Find the arithmetic mean of first ten even natural numbers.