Zero is a natural number.

A positive intezer is a natural number also.

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

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

Taking the set of natural numbers as the universal set, write down the complements of the following set: {x : x is a natural number divisible by 3 and 5}

Find the intersection of each of the following pairs of set :- A ={x : x is a natural number and multiple of 3} B = {x : x is a natural number less than 6}

Find the union of each of the following pairs of set : A = {x : x is a natural number and multiple of 3} B = {x : x is a natural number less than 6}