Question 13224
 Let S be the set of the 10 students.
 If T is a subet of S, for any element x (any student) of S, there are two
 possibilities,i.e. either x being in T, or x not in T.

 Hence, there are {{{2^10 }}} ways to form a subset T of S.

 In general, we call P(S) = {T | T is a subset of S} the power set of S.
 The size (cardinality) of P(S) is {{{2^n }}} if |S| = n.

 Kenny