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>This is fag packet math Is this what they call napkin math in the UK? Back of the cigarette pack math?

• dboreham 6y ago
  To be consistent I think it should be "fag packet maths".
• 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".