1. ## Probability

Our city has 2400 subscribers for HipHop magazines Of these, 1200 subscribe to Magazine A, 500 subscribe to Magazine B, and 100 subscribe to both. What is the probability that a subscriber selected at random subscribes to either Magazine A or B?

If I add the subscribers of magazine A and B together (which is 1700), and divide it by the total amount of subscribers then I get a very small fraction, which isn't right. I think.

2. You are trying to find $P(A \cup B) = P(A) + P(B) - P(A \cap B)$ or $\frac{1200}{2400} + \frac{500}{2400} - \frac{100}{2400} = \frac{1600}{2400} = \frac{2}{3}$.

3. $P(A)+P(B)-P(A \;\ and \;\ B)$

See how it's done?. You have to subtract the 100 they have in common. Otherwise, you'd over count.

$\frac{1200}{2400}+\frac{500}{2400}-\frac{100}{2400}$