Sets 3
2 marks · EasyIn a class, n(A) = 18, n(B) = 12, and n(A ∩ B) = 5. Find n(A ∪ B).
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25 (±0)
Common mistakes: Adding n(A) and n(B) without subtracting n(A∩B)
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Marking points
M1 · 1 mark · Applies the correct formula: n(A ∪ B) = n(A) + n(B) − n(A ∩ B)
A1 · 1 mark · Carries out calculation 18 + 12 − 5 = 25 (follow-through)
Worked solution