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Question
There are 260 persons with skin disorders. If 150 had been exposed to chemical A, 74 to chemical B, and 36 to both chemicals A and B, find the number of persons exposed to Chemical B but not Chemical A
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Solution
Let A = set of persons exposed to chemical A
B = set of persons exposed to chemical B
X = set of all persons
∴ n(X) = 260, n(A) = 150, n(B) = 74, n(A ∩ B) = 36
No. of persons exposed to chemical B but not to chemical A
= n(A' ∩ B)
= n(B) – n(A ∩ B)
= 74 – 36
= 38
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