Thrice stupid but not forever dumb

Today I felt very stupid on 3 occasions.
This morning I found that after lending my laptop to someone the night before they had watched a DVD on it - I thought the sound was broken and that after exaustive checking for software volume things that the problem was with a slider thing on the side and that the person who I had lent it to had found this straight away. I had come to the conclusion that the sound driver was broken because it was coming out realy realy quiet and had to be boosted on headphones to be heard at all.
In core maths I got my indicies muddled up and ended up with 6^-3/2 - 6^3/2 = k rather than 6^3/2 - 6^3/2 = k = 0 and the problem was not managing to do 2 - 1/2 which is pretty stupid.

After deciding that my bedroom floor was much to dirty and I would have to hoover it, going and finding a hoover in a cupboard and carefuly hoovering the floor (and the desk because it was getting dusty in places) and taking the hoover back to the cupboard where I found the cleaner who said that she was going to clean my room tomorow this made me feel very stupid.

But I got 23/24 in my chemistry test and got my little fighters AI in my computer game to make it so that they only shoot if they are pointing near the enemy (to within 40 degrees each way) the only bug with that is that it does not shoot if it is pointing at the second nearest one but not the nearest 1 ( but when it is attacking it is pointing at the nearest one so this won't matter unless the fighter is being attacked from multiple directions anyway - and with object avoidance and being shot at from each side it is probably dead anyway) Not dumb just sometimes stupid.