for one thing, you can't get partial credit for ideas/work that only exists in your head. (Similar to why it's a good idea to show work on homework assignments

for one thing, you can't get partial credit for ideas/work that only exists in your head. (Similar to why it's a good idea to show work on homework assignments and tests) If they sat there for a bit thinking about the problem and then provided a solution, I'm sure that would be fine. But that's not the situation he was describing.