if P(E)= 0.3 and P(F)= 0.4 and P(EunionF) = 0.1 then P(E U F)=

Question

The symbol for the union is the upside down U but I couldn't find it to type it. I am not sure what the formula for this problem is.

Answer 1

P(E) + P(F) - P(E and F) = P(E or F) or is union, and is intersection. Do a Venn diagram (two circles that intersect) and you see that adding the two circles areas (probabilities) doubly counts the intersection, so it must be subtracted. The probabilities just add if there is no intersection (They are independent)