Question

8) Use the formula for the cardinal number of union of two sets

n(AUB) = n(A) + n(B) – n(An B)
n
to solve the problem.
Set A contains 10 elements, set B contains 5 elements and 3 elements are common
to sets A and B. How many elements in the union of these two sets?
18
09
12
15

Answer 1

12

Explanation:

n(AUB) = n((A) + n(B) – n(AnB)

Step 1:

Identify the values for each function of the formula. n(A) = 10, n(B) = 5, n(AnB) = 3

Step 2:

Replace each function with its values

n(AUB) = n(A) + n(B) – n(AnB)

n(AUB) = 10 + 5 – 3

Step 3:

Carry on the simple arithmetic

n(AUB) = 10 + 5 – 3 (follow the BODMAS method)

= 15–3

= 12

Therefore, the n(AUB) is 12