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Infection A and B

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Infection A and B

by sang5650 » Fri Jan 15, 2010 1:44 pm
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

What do you think the answer is?
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by ace_gre » Fri Jan 15, 2010 2:00 pm
Hi, I find it easier to substitute numbers for N. Here it has to be divisible by 5 and 3...So I pick 15.

If N=15, then 1/3 have A ==>5
Of 5 having A, 1/5 have B==>1

Only 1 out of 15 have both A and B. rest 14 do not have A and B. i.e 14 N /15.
IMO D
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by sang5650 » Fri Jan 15, 2010 2:41 pm
Thanks got u!

Was trying to use a venn diagram to solve this..
I interpreted the question as having to find individuals not infected with A or not infected with B.
ur explanation makes sense.
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