Sixty percent of the students at a certain school wear neither a ring nor a necklace. Twenty percent wear a ring and 30 percent wear a necklace. If one of the students is chosen randomly, what is the probability that this student is wearing (a) a ring or a necklace? (b) a ring and a necklace?
+1223 We can make a Venn Diagram:
[ring || both || necklace] neither
[20%|| x% || 30% ] 60%
a) probability that the student is wearing a ring or a necklace:
1 - 60% = 40%
b) probability that the student is wearing a ring and a necklace:
20 + 30 - x + 60 = 100
110 - x = 100
x = 10%
