Number of sub-sequences in a given sequence

Question

If I am given a sequence X = {x1,x2,....xm}, then I will have (2^m) subsequences. Can anyone please explain how can I arrive at this formula intuitivel

Answer 1

Each subsequence is defined by choosing between selecting or not selecting each of the m elements. As there are m elements, each with two possible states, you get 2^m possibilities.