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anyone knows how to solve this DS? help guyzz

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anyone knows how to solve this DS? help guyzz

by reka » Sun Aug 29, 2010 2:43 am
In a test for the presence of a certain chemical in water, a true result is one that is positive when the chemical is present and negative when the chemical is not present. In tests of the water in 1,000 homes, how many of the test results were not true?

(1) 1 in 10 of the positive results were not true.
(2) 90% of the results were negative
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by sirisha.g » Sun Aug 29, 2010 3:11 am
IMO E.

using statement 1) u will not get the total number of positive results and hence you will not get the number of false results.
using statement 2) you know that 900 are -ve and 100 are +ve. but no info about false results.

using both. u know 900 are -ve, 100 are +ve out of which 10 are not true. but you donot know the number of false results among negative ones

whats the OA?
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by reka » Sun Aug 29, 2010 10:57 pm
OA is [spoiler](E)[/spoiler]
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