.
(a) We should check if P (E1 & E2) = P(E1)*P(E2).
Calculation P(E1) is easy: P(E1) = , since there are 6 outcomes for the first die,
showing the numbers 1, 2, 3, 4, 5 and 6 with equal probabilities.
To calculate P(E2), notice that the sum of 6 of two dice can be obtained in 5 (five) cases
(1,5), (2,4), (3,3), (4,2) and (5,1),
So the event E2 has the probability P(E2) = .
Now, the event (E1 & E2) is the intersection of E1 and E2;
in other words, first die shows a "3", while the sum of the faces of the two dice is 6.
It may happen if and only if BOTH dice face up a "3" -- the event with the probability , obviously.
Thus we have P(E1) = ; P(E2) = and P(E1 & E2) = .
The product of probabilities P(E1)*P(E2) = } = is not equal to P(E1 & E2) = --
hence, the two events E1 and E2 ARE NOT INDEPENDENT. ANSWER
(b) If the first die faces up a "3", then the sum is even in these 3 (three) cases
(3,1), (3,3), (3,5).
So the probability for S to be an even number is = . ANSWER
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If you want to learn this subject wider and deeper, look into my lesson
- Rolling a pair of fair dice
in this site.