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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?

 Feb 7, 2020
 #1
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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%

 Jan 29, 2022

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