Question

There are 200 individuals with a skin disorder, 120 had been exposed to the chemical A, 50 to chemical B and 30 to both chemical A and B, Find the number of individuals exposed to

1. Chemical A but not chemical B.

2. Chemical B but not. chemical C.

3. Chemical A or chemical B. 

Answer 1

1. Given; n(U) = 200; n(A) = 120;

n(B) = 50; n(A∩B) = 30

n (Chemical A but not chemical B)

= n(A ∩ B’) = n(A) – n(A ∩ B) = 120 – 30 = 90

2. n (Chemical B but not chemical A)

= n(A’ ∩ B) = n(B) – n(A ∩ B) = 50 – 30 = 20

3. n (Chemical A or chemical B)

= n(A ∪ B) = n(A) + n(B) – n(A ∩ B)

= 120 + 50 – 30 = 140.