Nobody has done anything wrong. I am not angry but I do want to cool this off before anything does happen. Change the thread to a jumble or something else you like. I will open it and delete all the comments.
In mathematics, you don't understand things. You just get used to them.
I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.