Posted by **Jim** on Sunday, October 14, 2012 at 2:14pm.

Could someone help be understand the general addition rule for probability? It says P(A or B)= P(A)+P(B) - P(A and B). But I get a different answer when I work it out myself:

P(A or B)= P(A)(1-P(B)) +P(B)(1-P(A))

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

=P(A) +P(B) -2P(A)P(B)

Would someone please help me! Thanks :)

## Answer this Question

## Related Questions

- Math- Still Don't Understand! - I do not understand how to work this problem out...
- math - Working on exploring algebra: Whats the Rule I understand the rules of In...
- math,correction - can someone correct this for me. Directions: Solve the ...
- Grammar and Composition - I don't understand how i can write a 1-2 minute speech...
- General - Please understand that I am not upset with anyone or whatever I just ...
- Math - There is exactly the same number of lollies in 10 different colours in a ...
- 4th grade - Exploring Algebra: What's the rule? You can find patterns to figure ...
- Algebra - Could someone work this out for me? Someone says the answer is 2.34 x ...
- Math - I don't understand this it says If the average of 6 numbers was 58, what ...
- finite math - A probability experiment was conducted in which the sample space ...