Question

How can I tell which of the 6 basic rules of probability to use?

Answer 1

i have never in my life heard of f the 6 basic rules of probability to use, but i can give you some advice
before starting to solve a probability problem make sure you understand exactly what it is asking
do not start thinking about "formulas" or such until you know exactly what you are trying to find
this will make your life much easier in this regard
for example
an urn contains 4 red balls and 6 blue ones. you select one, throw it out, select another
what is the probability that the second ball selected is blue if the first one selected is red?

forget formulas
you know the first ball was red, so there are still 6 blue ones and 9 left in the urn
you get \(\frac{6}{9}\) without appealing to any formula, but rather by thinking

Answer 2

Formula for two events that are independent: Pr(A) x Pr(B) = Pr(A n B)
Learn how to apply that; the other formulas can be easily derived in my opinion