Probability Prob,Given P(A)=0.5, P(A U B)=0.8 and P(A ∩ B)=0.1. Find P(A/B).

[bcahmel]

Homework Statement

Given P(A)=0.5, P(A U B)=0.8 and P(A ∩ B)=0.1. Find P(A/B).

Homework Equations

EQ 1: P(A U B) = P(A) + P(B) - P(A ∩ B)
EQ 2: P(x/y)= P(A ∩ B) divided by P(B)

The Attempt at a Solution

Immediately my first thought is to solve for P(y). So using EQ 1, I solve for P(B) by plugging the variables in, which resulted in 0.4. Is this right so far?
Once I did this I just used EQ 2, dividing 0.1/0.4 to get 0.25, which was my answer.

 

[rock.freak667]

I did not check your numbers, but your method is correct.

 

[bcahmel]

thank you! that's all I wanted to know :)