@LovesTha @mhoye 5<->8 also provides the same-ish error term. In English, it helps that kilometers get measured in multiples of 8 for some unknowable reason.
(Oh! You could do both, average them, and come out basically dead on! Just need to remember enough Fibonacci numbers to cover the face of a circular slide rule first…)
@xek @LovesTha where are you, that kilometres are in multiples of eight? I’ve never seen that.