Question

There are 260 persons with skin disorders. If 150 had been exposed to the chemical A, 74 to the chemical B, and 36 to both chemicals A and B, find the number of persons exposed to Chemical A but not Chemical B.

Answer 1

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 A but not to chemical B

= n(A ∩ B')

= n(A) – n(A ∩ B)

= 150 – 36

= 114