Question

Let a = {1, 2, 3, 4, 5} b = {1, 3, 5} c = {4, 6}. find the cardinality of the given set. 33. n(a) 34. n(b) 35. n(a ⋃

Answer 1

$n(a)=5\\ n(b)=3\\ n(a\cup c)=6\\ n(a \cap c)=1$

Answer 2

1) n(a) = 5

The cardinality of a set is the number of elements in that set. So, you simply need to count how many elements belong to the set, and the answer is 5

2) n(b) = 3

Simlarly, in this case you need to count how many elements belong to the set, the answer is 3

3) n(a ⋃ c) = 6

The union of two set is a set composed by all the elements belonging to either one of the sets, with no repetitions. So, since the first set contains all numbers from 1 to 5, the second set contains a 4, which however already belonged to the first set, but also a 6, which is added in the union. So, a ⋃ c = {1,2,3,4,5,6}, and thus n(a ⋃ c)=6.

4) n(a ⋂ c) = 1

The intersection of two sets is a set composed by the elements belonging to both sets. So, 1,2,3 and 5 don't belong to the intersection, because they belong to the first set alone, while 6 doesn't belong to the intersection because they don't belong to the first one. So, a ⋂ c = {4}, and thus n(a ⋃ c)=1.