Answer :
Answer:
.2
Step-by-step explanation:
Let A represent the probability a band member plays clarinet.
Let B represent the probability a band member is in the woodwind section.
These two events, A and B, are not mutually exclusive, because you can be a clarinet and be in the woodwind section. (Of course! Clarinet gang for life.) They are not independent, because if a band member is a clarinetist, they must be in the woodwind section.
So P(B) = .4
P(A|B) = .5
The question is asking us for the probability a band member is in the woodwind section and plays clarinet, or P(A and B).
We can figure out P(A and B), also known as the intersection, by using this formula:
P(A|B) = P(A and B) / P(B)
.5 = P(A and B) / .4
P(A and B) = .2
In case this was too much algebraic thinking, you can also think about it in your head without using formulas. 40% of the band are woodwinds, and 50% of the woodwinds are clarinets, so 20% of the band are clarinetists who are in the woodwind section. Easy!