What fraction of the students in a class have blue eyes?
1) 10% of the girls have blue eyes.
2) 20% of the boys have blue eyes.
The OA is E.
Please, can any expert explain this DS question for me? I have many difficulties to understand why that is the correct answer. Thanks.
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What fraction of students in a class have blue ayes?
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Jay@ManhattanReview
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Clearly, each statement alone is insufficient. So, let's combine them.swerve wrote:What fraction of the students in a class have blue eyes?
1) 10% of the girls have blue eyes.
2) 20% of the boys have blue eyes.
The OA is E.
Please, can any expert explain this DS question for me? I have many difficulties to understand why that is the correct answer. Thanks.
(1) and (2) together
Say the number of boys = b, thus, the number of boys with blue eys = 10% of b = 0.1b; say the number of girls = g, thus, the number of girls with blue eys = 20% of g = 0.2g
The number of students in the class with blue eyes = (01.b + 0.2g)
The fraction of students that have blue eyes = (01.b + 0.2g) / (b + g). We can't get the answer. Insufficient.
The correct answer: E
Hope this helps!
-Jay
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