I) Suppose there are 1000 students living in a certain dorm on Busch campus, of
ID: 2921223 • Letter: I
Question
I) Suppose there are 1000 students living in a certain dorm on Busch campus, of whom 600 are CS majors, 200 are Stat majors, 100 are Math majors, 90 are CS & Stat double majors 50 are CS & Math double majors 60 are Stat & Math double majors, and 20 are CS & Stat&Math; triple majors (these are also considered double majors). What is the probability that a randomly selected student living in this dorm is... a) ...majoring in at least one of CS, Stat or Math? b)...majoring in Math or double majoring in CS & Stat (Hint: words can play the role of parentheses)Explanation / Answer
A) number of Students majoring in at least majors + stat majors + math majors - cs and stat - cs and math - stat and math + all three
= 600 + 200 + 100 - 90 - 50 - 60 + 20
= 720
P(majoring in at least one) = 720/1000 = 0.72
B) P(majoring in math or double majoring in CS and stat) = P(majoring in math) + P(double majoring in cs and stat) - P( majoring in math and double majoring in cs and stat)
= 100/1000 + 90/1000 - 0
= 0.19