Student [who had failed a pre-test just a week earlier]: "Mister, if I know how to do these, do I need to show my work? Or can I just write the answer?"
Me [looking at the problems on the board with the answers already posted]: "Sure, but I can't even do some of these in my head. Can you walk me through how you would do number 14?"
Student [hesitating]: "Fourteen?"
Me: "Yes."
Student: "Well, I would break down 21 into 3 and 7. And the 210, I would divide by 2 and get...105."
Me [trying to keep 3, 7, and 2 in my memory while trying to factor 105]: "Good. Keep going."
Student: "But the 105, nothing goes into that and since there's nothing in common..."
Me: "But 105 is divisible by something, so you can't just say that you're done. What's it divisible by?"
Student: "Um...it's divisible by some number."
Me: "Some number? Yeah. You're going to have to show your work to get credit." (8/23/21)