What book can I read to understand probability?
If a six-sided die is rolled three times, what is probability that the die will land on an even number exactly twice and on an odd number exactly once?
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Answers ( 1 )
Probability is tricky. I don't know your age or your mathematics background, and it's difficult to jump into ANY probability question without knowing what your "tree of knowledge" in math looks like.
So I'll say this: probability questions are almost always of the form "how many successful possible outcomes can I have?" and "how many TOTAL possible outcomes can I have?" -- and then your answer is the first number divided by the second. So really, they're almost always combinatorics questions -- after all, a calculator makes the division part very easy (and the second number, the total, is usually not too hard, either: in this case, you can roll the die six ways, as you can with the second and third roll, so there are 6x6x6 = 216 total possibilities).
But the combinatorics -- the counting of "how many ways" -- can be very difficult, because you have to think about your problem in just the right way to avoid undercounting or overcounting the scenarios. You could roll a 2 first, then a 6, then a 1 -- and that's a success! But is that different from rolling a 1, then a 2, then a 6? You need to understand combinatorics to be able to say so (for this problem, the answer is "yes").
So what book can you read? Well, knowing nothing else about you, I think I'd recommend Khan Academy: it's free, it has video lessons and practice skills, and you can up or down in the "tree of knowledge" to fit your understanding of a topic. Khan isn't perfect by any means -- and when you run into a topic that it doesn't sufficiently explain, you should get help from a human -- but it's a good place to start.
https://www.khanacademy.org/math/statistics-probability/probability-library