Math Is Fun Forum

thanu_hello

Member

Registered: 2007-02-13

Posts: 5

Problem in SET THEORY

I have a problem, if u have a solution let me know.

In a sample survey it is found that 53% prefer brand A, 61% brand B, 60% brand C, 24% prefer AB, 35% prefer BC, 27% prefer AC and 5% prefer none. Find how many prefer all the three?

Please help me

Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Re: Problem in SET THEORY

Remember that:
(A or B or C) = (A) + (B) + (C) - (A and B) - (A and C) - (B and C) + (A and B and C)
You want to find (A and B and C).
Also remember that (A or B or C) should be 5 less because 5% prefer none.

thanu_hello

Member

Registered: 2007-02-13

Posts: 5

Re: Problem in SET THEORY

Remember that:
(A or B or C) = (A) + (B) + (C) - (A and B) - (A and C) - (B and C) + (A and B and C)
You want to find (A and B and C).
Also remember that (A or B or C) should be 5 less because 5% prefer none.

so is (A or B or C) = 95%

Toast

Real Member

Registered: 2006-10-08

Posts: 1,321

Re: Problem in SET THEORY

Uh yeah, at least that's how I did it. However, I haven't done problems like this with percentages, only with integer values, however I think if u get percentages you can just think of each percentage as x% out of 100 people.

I'm not certain though.

thanu_hello

Member

Registered: 2007-02-13

Posts: 5

Re: Problem in SET THEORY

I think what u told is correct. Thanks a lot Toast.