Given that the probability a student passes their exams is three out of eight, what is the probability the student fails?
So out of all of the students, they will either pass or they will fail. So if we know three out of eight will pass their exam, eight out of eight must represent all of the students because that’s 100 percent. So how many out of eight would fail? Well, three-eighths plus something over eight is equal to eight over eight.
And when adding fractions, we keep our denominator and we add our numerators. So three plus what gives us eight? That would be five because five plus three is equal to eight.
So the probability that a student fails their exams will be five out of eight, which is not very good. That’s over half they expect to fail their exam.