In the lecture, the teacher writes on the Board and then one student says to another...

Yesterday I came to a physics lecture with a delay of five minutes. I went to the office, and there all as usual: noise and random movements of classmates. Went to my seat, sat down, the teacher just started on the Board to write some furious formula.

Everyone fell silent, her carefully written off. And then I corner of my eye noticed that my neighbor made a formula error.

— What you are writing, you idiot?! — cut through the silence in the office my cry. That's my word, not wanted as loud accident happened...

— No, that sounds about right... — thoughtfully said the teacher, moving away a few paces from the Board and carefully looking at the formula.

via factroom.ru