-
Pugalenthi
- Junior | Next Rank: 30 Posts
- Posts: 29
- Joined: Fri Sep 25, 2009 9:26 am
A marketing firm determined that, of 200 households surveyed, 80 used neither brand A nor brand B soap, 60 used only brand A soap, and for every household that used both brands of soap, 3 used only brand B soap. How many of the 200 households surveyed used both brands of soap?
(a) 15
(b) 20
(c) 30
(d) 40
(e) 45
Here is my logic (applying the venn diagram logic)...
P(A u B) = p(A) + p(B) - p(A n B) + neither p(A n B)
200 = 60 +3x -x +80
2x = 60
X = 30
But the answer given in the book is A. What am I missing? Any help would be much appreciated.
(a) 15
(b) 20
(c) 30
(d) 40
(e) 45
Here is my logic (applying the venn diagram logic)...
P(A u B) = p(A) + p(B) - p(A n B) + neither p(A n B)
200 = 60 +3x -x +80
2x = 60
X = 30
But the answer given in the book is A. What am I missing? Any help would be much appreciated.
