Complete question :
At a certain school, 25% of the students wear a watch and 30% wear a braclet. 60% of the students wear neither a watch nor a braclet. (a) One of the students is chosen at random. What is the probability that this student is wearing a watch or a braclet (b) What is the probability that this student is wearing both a watch and a bracelet?
Answer:
0.40 ; 0.15
Explanation:
Given :
w = watch
b = bracelet
P(w) = 0.25
P(b) = 0.3
P(w' U b') = 0.60
Probability that student is wearing a watch or a bracelet :
P(w U b) = 1 - P(w' U b')
P(w U b) = 1 - 0.60
P(w U b) = 0.4
Probability that student is wearing a watch and a bracelet :
P(w n b) = p(w) + p(b) - p(w U b)
P(w n b) = 0.25 + 0.3 - 0.4
P(w n b) = 0.55 - 0.4
P(w n b) = 0.15