Question

A test has 5 questions. For each question the answer is either correct or incorrect. How many outcomes have more than one correct answer?

Answer 1

It's binary arithmetic :)
Your answers can have two possible values, right or wrong. That means there are 2^5 (32) possible combinations of right or wrong answers.

The outcomes that have only one correct answer are the ones where only answer 1, or 2, or 3, or 4, or 5 is correct (were only one of the bits is true). That's 5 possible combinations with only one correct answer.

Answer 2

But you also need to consider the case of all incorrect answers, so that's the 6th possibility that falls into "not more than one correct answer".
So the result should be 32 possibilities minus 6 with equal to or less than one correct answer.

Answer 3

Thanks:)