On the AMC, a correct answer earns points, while both a wrong answer and a blank earn (roughly) the same low or zero score — there’s no extra penalty for guessing wrong beyond not gaining points. That changes the math on whether to guess.
Quick elimination heuristics
- Parity: if the answer must be even (or odd) by the structure of the problem, cross out choices of the wrong parity.
- Sanity on magnitude: an area or length can’t be negative; a probability can’t exceed 1.
- Monotonicity: if you can tell whether the true answer should be larger or smaller than some reference value, eliminate choices on the wrong side.
- Quick test cases: plugging in a simple special case sometimes rules out several choices at once.
The guess/skip decision
As a rule of thumb: skip a problem only if you have zero eliminations and truly no insight. With even one choice eliminated, the expected value of guessing among the rest is positive compared to leaving it blank. With two or more eliminated, guessing is clearly worth it.
Applying it
Scenario: A problem asks for the area of a region, and you’re out of time to fully solve it. The answer choices are (A) −12, (B) 8, (C) 15, (D) 24, (E) 40.
Response: Immediately eliminate (A) — an area can’t be negative. If a rough estimate suggests the region is smaller than a reference square of area 20, you can further eliminate (D) and (E), leaving a guess among just two choices.
Practice problems
1.A problem's answer must be an odd integer. The choices are 12, 15, 18, 21, 24. How many choices can you eliminate immediately, and which remain?
2.You've eliminated 1 of 5 answer choices on a problem you don't know how to solve. Should you guess among the remaining 4, or leave it blank?
3.A problem asks for a probability, and one answer choice is 5/4. Can you eliminate it, and why?
4.Why does the AMC's scoring system (unlike some exams with a guessing penalty) make it almost always worth guessing when you can eliminate at least one choice?