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There are 34 plant species found on a certain salt marsh. A nearby industrial in

ID: 3074147 • Letter: T

Question

There are 34 plant species found on a certain salt marsh. A nearby industrial installation releases three airborne chemicals, A, B, and C. 14 of the species found on the marsh are sensitive to chemical A, 12 are sensitive to chemical B, and 10 are sensitive to chemical C Also, 8 species are sensitive to both chemicals A and B, 7 to both A and C, and 6 to both B and C. Finally, 3 species are sensitive to all three chemicals. If a plant is selected at random, what is the probability that it is a) sensitive to the chemicals released by the industrial installation? b) not sensitive to chemical B? c) sensitive to either chemical A or chemical B? d) sensitive to either chemical A or chemical C? e) not sensitive to any of the chemicals released?

Explanation / Answer

from above:

a)N(sensitive to chemicals)

b)

N(not sensitive to chemical B )=34- N(sensitive to chemical B )=34-12 =22

c)

N(sensitive to A or B) =N(A)+N(B)-N(A n B) =14+12-8=18

d)

N(sensitive to A or C) =N(A)+N(C)-N(A n C) =14+10-7=17

e)

Not sensitive to any chemical =N(T)-N(AUB UC) =34-18=16

N(T)= 34 N(A)= 14 N(B)= 12 N(C)= 10 N(AnB)= 8 N(BnC)= 6 N(AnC)= 7