Answer:
a. 16
b. 24
c. 9
d. 256
Step-by-step explanation:
Let cardinality of the set A .
Any subset of A can contain i elements.
Now these i elements can be chosen in ways. So the number of subsets can be written as,
a. Here we have n = 4. So the Total no. of subsets = .
b. The no. of permutations is n! for any set with cardinality n. So, here it is = 4! = 24
c. Let denote the set consisting of all permutations of A where i is fixed, . Using symmetry, (fix one element and permute the rest) is the same . Also (fix 2 elements and permute the rest).
By similar arguments, and .
Recall the Principle of inclusion exclusion,
Note that is the set containing permutations with at least one fixed point. So we require 4! - S.
Computing S.
Required answer is 4! - S = 24 - 15 = 9
d. In general the no. of functions from A (|A| = n) to B (|B| = m) is given by, . Any element of A can be assigned to any of the m elements in B, so the possibilities are .
Here m = n = 4. So the answer is .