MCQ
If A = {2, 3, 4, 5, 7}, B = {7, 8, 9}, then find n(A ∪ B).
- A1
- B3
- C5
- D7
Solution:
A = {2, 3, 4, 5, 7}
n(A) = 5
B = {7, 8, 9}
n(B) = 3
n(A ∩ B) = 1
$\therefore$ (A ∪ B) = n(A) + n(B) − n(A ∩ B)
(A ∪ B) = 5 + 3 − 1 = 7
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