Addition rule
Also written: or rule
To get P(A or B), add P(A) and P(B), then subtract P(A and B), because the cases where both happen were counted twice. For mug (0.3) and express (0.2) it gives 0.44.
Also written: or rule
To get P(A or B), add P(A) and P(B), then subtract P(A and B), because the cases where both happen were counted twice. For mug (0.3) and express (0.2) it gives 0.44.