Should you guess on the SAT? The answer lies deep within this fake SAT question:

This question describes what happens when you guess blindly on any SAT question. If you have five possible answer choices and choose one at random, you have a 20 percent chance of choosing the right one. In other words, if you were to randomly pick an answer on five of these multiple-choice questions without even looking at the answer choices, you’d probably get one question right for every five guesses you made.

Now think back to the .25 of a point taken from your raw score for each wrong answer. This “penalty” isn’t some random number. It’s strategically designed to eliminate any gain you might get from guessing randomly. If you guess randomly on five questions, getting one right and four wrong (as probability states you will), your raw points for those five questions will work out to

This adds up to a grand total of 0 raw points. So guessing’s a waste of time, right? WRONG. Read on.

Guessing’s a waste of time if you’re guessing among five answer choices. But there’s no rule saying you have to guess among five answer choices. If you know how to guess wisely, how to eliminate answer choices before guessing, the game changes. Take the following Sentence Completion question:

We used this example because we thought you may not know the meanings of the words anthropomorphic, sanguinary, sesquipedalian, or sententious. All four of these words are more obscure than the vocabulary that usually appears on the SAT. But you probably do know the meaning of delicious and can tell immediately that it does not fit correctly into the sentence (a delicious dog?).

True, you still don’t know the right answer. All you’ve done is eliminate one answer choice. But once you’ve eliminated delicious as a possible answer, you only have to guess between four rather than five choices. If you guess among these four choices, you’ll get one question right for every three you get wrong.

This adds up to a grand total of .25 raw points. In other words, if you can eliminate just one answer as definitely wrong, the odds of guessing shift to your favor. And every point or fraction of a point you can jam into your raw score is worthwhile.

All this explanation adds up to The Grand Rule of Guessing:

Some students out there have a thing against guessing. They have this feeling that guessing is cheating. They think guessing rewards people who don’t know the answer and are just playing games with the SAT.

If you’re one of those students, get over it. First, by not guessing you’re hurting your own test scores. Second, guessing intelligently is just a form of partial credit. We’ll use the example of the Sentence Completion question about the dog guarding Hades to make this point.

Most people taking the test will only know the word delicious and will only be able to throw out that word as a possible answer, leaving them with a one in four chance of guessing correctly. But let’s say that you knew that sententious means “given to pompous moralizing” and that no hound spouting pompous moral axioms would be guarding the gateway to the Greek underworld. Now, when you look at this question, you can throw out both delicious and sententious as answer choices, leaving you with a one in three chance of getting the question right if you guess.

Your extra knowledge gives you better odds of getting this question right, just as extra knowledge should.

There’s no penalty on grid-in Math questions. If you guess and get one wrong, you won’t lose any points. But, and this is a big “but,” the odds of randomly guessing the right answer on a grid-in is around ¹/ ₁₄₄₀₀. Even without the guessing penalty, these low odds mean that if you have no idea what the answer to a grid-in question is, there’s not much value in taking a wild guess.

If you have worked out a grid-in problem, and have an answer, grid it in. Even if you’re unsure of the answer, gridding it in can’t hurt.