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what does she reads

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what does she reads

by maihuna » Fri Aug 14, 2009 11:34 am
In a hostel, 60% of the students read French news paper, 40% read English news paper and 20% read both french and English news papers. A student is selected at random. Find the probability that she reads neither french nor English news papers.
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by DanaJ » Fri Aug 14, 2009 11:42 am
students who read French papers = students who read only French papers + students who read both = 60% --- this means that the students who read only French papers = 60% - 20% = 40%.

students who read English papers = students who read only English papers + students who read both = 40% --- the students who read only English papers will be = 40% - 20% = 20%.

Total = 40% + 20% + 20% + with x = students who read neither.

x = 100% - 80% = 20%.

Probability = 0.2
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Re: what does she reads

by dtweah » Fri Aug 14, 2009 11:54 am
maihuna wrote:In a hostel, 60% of the students read French news paper, 40% read English news paper and 20% read both french and English news papers. A student is selected at random. Find the probability that she reads neither french nor English news papers.
Let E event a student speaks english

F french event student speaks French

Then P(E)=.6, P(F)=.4, P(E and F)=.2

We want P( E^c and F^c), where E^c is the complement of E

By DeMorgan's Laws ( E^c N F^c) = (E U F)^c

So P( E^c N F^c)= P(E U F)^c= 1-P(E U F) = 1- (P(E)+ P(F) - P(E and F))

1- (.6 +.4-.2)= .2=1/5
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