# Is the book wrong or me?

it's my first question on this forum.

I just purchased Probability and Statistics - Basic book from amazon to refresh and learn what I've never learned. I like the book it explains the subject well. However, I got a different result on one of the examples.

Example: 2 fair dice are rolled. What is the probability of getting a sum less than 7 or a sum equal to 10?

The books claims that P(A) = 15/36 and P(B) = 1/36. And base on that P(A or B) = 4/9.

I agree on P(A) but I believe that P(B) should be equal to 3/36, including {(4,6), (5,5), (6,4)} rolls. Therefore, my final result is P(A or B) = 3/6.

Am I missing something or the book got it wrong?

• Two comments. P(A and B)=0, the question asks about P(A or B). In this link they make the same mistake you mention. – user10525 Apr 28 '12 at 17:25
• I already corrected the question per gung note. It looks like it's the same book. Thanks for the link. Now I have an online version too. – Vadim Apr 28 '12 at 17:35