chandak_anand Posted March 20, 2009 Share Posted March 20, 2009 During the past week, a local medical clinic tested N individuals for two infections. If 1/3 of those tested had infection A and, of those with infection A, 1/5 also had infection B, how many individuals did not have both infection A and B? A) N/15 B) 4N/15 C) N/5 D) 14N/15 E) 4N/5 Quote Link to comment Share on other sites More sharing options...
magnetronclassic Posted March 20, 2009 Share Posted March 20, 2009 IMO D - 14N/15 N/3 -A N/3*1/5=N/15- Both A and B So total not infected by both A and B = N-N/15=14N/15 Quote Link to comment Share on other sites More sharing options...
MBAchase Posted March 20, 2009 Share Posted March 20, 2009 solution: didn't have both means they can be infected by one or none. N - infected by both N - N/3 * 1/5 =14N/15 Quote Link to comment Share on other sites More sharing options...
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