Two dice are thrown together and the total score is noted. The events E, F and G are ‘a total of 4’, ‘a total of 9 or more’, and ‘a total divisible by 5’, respectively. Calculate P(E), P(F) and P(G) and decide which pairs of events, if any, are independent.
If two dice are thrown together, we have
n(S) = 36
Now, let’s consider:
E = A total of 4 = {(2, 2), (1, 3), (3, 1)} ⇒ n(E) = 3
F = A total of 9 or more
= {(3, 6), (6, 3), (5, 4), (4, 5), (5, 5), (4, 6), (6, 4), (5, 6), (6, 5), (6, 6)}
So, n(F) = 10
G = A total divisible by 5
= {(1, 4), (4, 1), (2, 3), (3, 2), (4, 6), (6, 4), (5, 5)}
So, n(G) = 7
It’s seen that (E ⋂ F) = Ø and (E ⋂ G) = Ø
And, (F ⋂ G) = {(4, 6), (6, 4), (5, 5)}
⇒ n(F ⋂ G) = 3 and (E ⋂ F⋂ G) = Ø
Hence, the probabilities if the events are