math
posted by tana on .
probability... two dice are tossed.... and their sum is recorded ..find probability p ( sum is between 2 and 9)

Add the probabilities of getting
I assume you want the probaility of getting 2 to 9 INCLUSIVE. You could add the probabilities of getting
2,3,4,5,6,7,8 and 9
OR,
subtract from 1, the probabilities of getting 10,11, or 12.
Let's do it the latter way, since it's quicker.
1  3/36  2/36  1/36 = 5/6
if you are wondering where the 3/36 came from, the probability of getting 10 is 3/36, since the ways of getting it are
5+5, 6+4 or 4+6, and there are 6*6 possible outcomes.