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27 Nov 2017, 09:12
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Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
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48% (01:30) correct
52%
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Is the probability of choosing a student in class X who has scored more than 50% marks in an exam greater than \(\frac{1}{4}\)?
(1) probability of choosing a boy in class X who has scored more than 50% marks in the exam is \(\frac{1}{2}\).
(2) probability of choosing a girl in the class X is \(\frac{2}{5}\).
(1) probability of choosing a boy in class X who has scored more than 50% marks in the exam is \(\frac{1}{2}\).
(2) probability of choosing a girl in the class X is \(\frac{2}{5}\).
27 Nov 2017, 18:44
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chetan2u
Is the probability of choosing a student in class X who has scored more than 50% greater than \(\frac{1}{4}\)?
(1) probability of choosing a boy in class X who has scored more than 50% is \(\frac{1}{2}\).
(2) probability of choosing a girl in the class X is \(\frac{2}{5}\).
self made
(1) probability of choosing a boy in class X who has scored more than 50% is \(\frac{1}{2}\).
(2) probability of choosing a girl in the class X is \(\frac{2}{5}\).
self made
so Q is :- P of picking a student scoring more than 50% >1/4??
lets see the statements
(1) probability of choosing a boy in class X who has scored more than 50% is \(\frac{1}{2}\).
Tells us about boys. nothing about girls..
insuff
(2) probability of choosing a girl in the class X is \(\frac{2}{5}\)
again info only about girls but doesn't tell us that how many girls score >50%
insuff
Combined
Easy to chose E as the numbers of both not known..
But always solve -
statement II tells us that girls are \(\frac{2}{5}\) , so boys are \(\frac{3}{5}\)
statement I tells us that 1/2 of boys scored more than 50%
so ATLEAST \(\frac{1}{2}*\frac{3}{5}=\frac{3}{10}\) scored more than 50%, even if none of the girls scored above 50%
\(\frac{3}{10}>\frac{1}{4}\), so ans is always YES
suff
C
06 Jan 2018, 08:52
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Question: if we know, that the probability of picking a boy (=student) who is better that 50%, do we really have to know any more information about the rest to answer the question?
In my understanding, the rest consists of a. boys below 50%, b. girls above 50%, c. girls below 50% (consolidated = other 50% of total of students).
Therefor I know, that whatever comes in addition, we for sure have a probability of greater 50% (if we have at least 1 girl who is better than 50%), and the given information in 1) is sufficient to answer. Because at least half of the total students are boys better than 50%.
If this is not the case the question is probably missleading the way it's stated.
Let me know what you think.
In my understanding, the rest consists of a. boys below 50%, b. girls above 50%, c. girls below 50% (consolidated = other 50% of total of students).
Therefor I know, that whatever comes in addition, we for sure have a probability of greater 50% (if we have at least 1 girl who is better than 50%), and the given information in 1) is sufficient to answer. Because at least half of the total students are boys better than 50%.
If this is not the case the question is probably missleading the way it's stated.
Let me know what you think.
