I did the same, but if I'm doing that skimming and I know the answer to question 12 is (c), I fill in (c) and keep going. I don't read all the questions, then go back and try and remember which of the questions I knew the answers to off-hand. Instead, I'd do the test in 3 passes.
1. Answer all questions that I know the answer instantly or (for math type tests) can solve within a few seconds. Skip anything not quick.
2. Go back and answer questions that I know I can solve. These usually take a minute or two (since the easy ones should already be done). If there happens to be a question I know I can solve but also know will take "too much time," skip it.
3. If there's time left, work through any remaining questions (hopefully there aren't that many), making a best effort to prioritize the ones I'm more confident that I can solve in the time remaining.
1. Answer all questions that I know the answer instantly or (for math type tests) can solve within a few seconds. Skip anything not quick. 2. Go back and answer questions that I know I can solve. These usually take a minute or two (since the easy ones should already be done). If there happens to be a question I know I can solve but also know will take "too much time," skip it. 3. If there's time left, work through any remaining questions (hopefully there aren't that many), making a best effort to prioritize the ones I'm more confident that I can solve in the time remaining.