Question

what is the sum of probability of an event and probability of that of complementary event​

Answer 1

The rule of complementary events comes from the fact the the probability of something happening, plus the probability of it not happening, equals 100% (in decimal form, that's 1). For example, if the odds of it raining is 40%, the odds of it not raining must equal 60%. And 40% + 60% = 100%.....