back-of-the-envelope calculation
(redirected from back of the envelope calculation)back-of-the-envelope calculation
A calculation or mathematical formulation that is approximated in a quick, informal, and rough manner, as might be sketched out on a scrap of paper (such as the back of an envelope). When it came time to pay the bill, we had to do some back-of-the-envelope calculations to figure out who owed how much.
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