1-when you are trying so hard to work out something far too complex for your state of mind at the present time that you get a headache.
2-when your so mentally exhausted thinking of minor simple things is a massive effort.
1-If there was a fence that was like a grid, and the total volume of the fence was 3ft cubed, and the fence was 6 foot tall. if the fence was evenly distributed and a dragonfly measuring 1” height and 4” width, and it could only fly up to 4', what is the probability it will hit the fence, flying straight at the fence, at any given point within the range given.
reading that gave me massive brainstrain
2- what is 5+5+5+5+7+5? too tired, giving me brainstrain