What is the probability of males liking or being neutral towards the commercial?

[maiad]

Finding probabilities through general addition rule

Homework Statement

http://postimg.org/image/q9ztktpot/

Homework Equations

P(A or B)=P(A)+P(B)-P(A and B)
P(A and B)=P(A)P(B)

The Attempt at a Solution

The question is for part b). It said it was only focused on the mens so i ignored all the other numbers.
I used the general addition rule where P(A or B)=P(A)+P(B)-P(A and B). Since these events are independent, i used this equation... P(A and B)=P(A)P(B). I found P(A) from 400/2000= 0.2
I found P(B) from 500/2000=0.25. Then i found P(A and B)=P(A)P(B)=0.05

Now i plugged it into the general addition rule... P(A or B)=0.2+0.25-0.05=0.4 but it was wrong.
What did i do wrong?

 

[pbuk]

The events are not independent, they are exclusive; if a man likes the commercial the probability that he is neutral is zero.

But you do not need probabilty theory to answer (b) anyway - it is a simple percentage question.

 

[maiad]

Would it just be (400+500)/2000 =0.45?

 

[pbuk]

Yes :)

 

[maiad]

is it because the two varibles can't overlap because their exclusive so we don't have to account for the everlap so we don't need to use the inclusion-exclusion rule?

 

[Ray Vickson]

is it because the two varibles can't overlap because their exclusive so we don't have to account for the everlap so we don't need to use the inclusion-exclusion rule?

Your question is impossible to answer, since you do not tell us what you mean by A and B, etc.

 

[maiad]

Let A be the males that like the commercial and B, the male that are neutral towards the commercial