3 ms·
From https://en.wikipedia.org/wiki/Back-of-the-envelope_calculation https://en.wikipedia.org/wiki/Back-of-the-envelope_calculati...: In British English, a simil
by hondo77 6y ago
From https://en.wikipedia.org/wiki/Back-of-the-envelope_calculation https://en.wikipedia.org/wiki/Back-of-the-envelope_calculati...: In British English, a similar idiom is "back of a fag packet".