Registry math: every formula on one page

How to work any math question

Every math question on the registry follows the same four steps. First, name what is changing: distance, grid, kVp, time or something else. Second, pick the formula for that change. Third, put the old value and the new value in the right places. Fourth, before you choose an answer, ask whether it moves the right way. More distance needs more mAs. A higher-ratio grid needs more mAs. More kVp needs less mAs. If your answer moves the wrong way, you flipped the ratio, and the answer choices usually include that flipped answer, so this check catches the most common mistake.