pman wrote:

in a consumer survey , 85% of those surveyed likes at least one of three products: 1, 2, and 3. 50% of those asked liked product 1, 30% liked product 2, and 20% like product 3. if 5 % of the people in the survey likes all 3 of products, what % of the survey participants likes more than one of the three products?

5

10

15

20

25

shouldn't the answer be 15?

let union = union of sets

int = intersection of sets

so

n(A union B union C) = n(A) + n(B) + n(C) - n(A union B) - n(B union C) - n(C union A) + n(A int B int C)

putting values

0.85 = 1 - [n(A union B) + n(B union C) + n(C union A)] + 0.05

or [n(A union B) + n(B union C) + n(C union A)] = 0.20

so people who like more than 2 is obtained by

[n(A union B) + n(B union C) + n(C union A)] - 2 [A int B int C]

= 25 - 10

= 15

What do you guys think?