Prove that number of subsets of a set containing n distinct elements is , for all n ϵ N.
To Prove:
 is the no. of subsets of a set containing n distinct elements.
Now, there is only one subset since for a null set there is only one element φ
Now, we’ll substitute different values for n,
At n = 0,
No. of subsets = 1 = 
If we consider a set that has 1 element then there will be 2 subsets that has 1 & φ
Thus, at n = 1, it is true
now at n=2
No. of subsets = 2 = 
Now, let us consider that there is a set  has k elements.
At n = k,
No. of subsets =  is true.
Now, for set , having k+1 elements,
Compared to the set , 
 has an extra element and thus will form an extra collection of subsets when combined with the existing 
 subsets & an extra 
 subset will be formed.
Thus, at n = k+1,
No. of subsets =  + 
                        = 2.
                        = 
Thus, by mathematical Induction,
 is the no. of subsets of a set containing n distinct elements.