#tired math

Okay, this is going to take a bit, please bear with me.

When I took my pill last night, I was wondering, how much water I had drunken with it, because I recently listened to a lecture where we were told that you should drink at least 100ml of water with your pills to make sure they really end up in your stomach. My bottle holds 750ml and has some weird percentages on its side (it used to be a smoothie bottle) so I could estimate, that I had drunken 15% of the bottle and now wanted to know if that was at least 100ml.

Now for the following to make sense you have to know, I'm home sick and a bit off my game, it was late last night and I was quite tired.

My tired math went as follows: 15 is 1/6.66666 of 100, so I needed to divide 750 by approximately 6.6, which I did in steps. 660 : 6.6 is 100 (90 left -> 66 + 24), 726 : 6.6 is 110 (24 left -> 19.8 + 4.2) 745.8 : 6.6 is 113 at which point I stopped, because it was over 100ml and I was falling asleep.

This morning I lay in bed not wanting to get up and significantly more awake and felt kind of stupid, because I could have just calculated 7.5 x 15 (75 + 5 x 7,5 = 75 + 37.5 = 112.5) and would have gotten a more accurate result way faster than I did the night before.