Some of the math competitions I participated would penalize for skipping around. You were awarded +5 for correct answers and -4 for incorrect or skipped questions. It was not uncommon for negative scores. In one test, any stray marks were also marked as incorrect. No erasing, no changing a 7 to a 9, or anything was allowed. The questions leaned toward an increasing difficulty, but there could something very difficult followed by a string of much easier questions. So additional math had to be done to see if it would be better to stop or skip.