Question

Use the following information:

U = x

A = x

B = x is a prime number greater than 5

(Note: The prime numbers less than 20 are 2, 3, 5, 7, 11, 13, 17, and 19.) Find the cardinality of each set.


Answer:

n (A'∪ B)

Answer 1

• n(U) = 20
• n(A) = 8
• n(B) = 5
• n(A'∪B) = 15

Explanation:

For these sets, it is easy enough to list the elements and count them.

U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20}

n(U) = 20

A = {1, 3, 5, 7, 9, 11, 13, 15}

n(A) = 8

B = {7, 11, 13, 17, 19}

n(B) = 5

A'∪B = {2, 4, 6, 7, 8, 10, 11, 12, 13, 14, 16, 17, 18, 19, 20}

n(A'∪B) = 15