Best way to approach a Multiple Choice exam I have an exam tomorrow with 100 multiple choice questions. Each question has 4 options, only 1 is correct.

If I answer the question and get it right, I get 1 mark.
If I leave it blank, I get 0.
If I answer incorrectly, I lose 0.25 marks.

How should one approach the test? Mathematically/statistically are my odds better if I guess if I don't know the answer?
Imagine if you had $4$ questions you don't understand.  

If you leave them blank, you will get a mark of $0$.
If you guess all of them, the expected result is getting $1$ right and $3$ wrong. This will get you an expected mark of: $$1-3(0.25)=0.25$$

Therefore it is better to guess than to leave questions blank.
If you can eliminate at least one choice on a question, then you should guess from the remaining choices.