Sum is always 1
Step-by-step explanation:
The sum of probability of an event and its complementary event is always 1.
Here, the event is rolling an even number. Let it be P(even)
Its complementary event is rolling a number that is not even. Let it be P(not even)
P(even) = 1/6
P(not even) = 5/6
P(even) + P(not even) = 1/6 + 5/6 = 1