Notam:
n = numarul
n : 4 = n - 21
n - n : 4 = 21
n |___|___|___|___|
n:4 |___|
Avem 4 segmente egale - 1 segment egal = 3 segmente egale = 21
21 : 3 = 7 (un segment egal)
n = 7 × 4 = 28 (numarul de referinta)
n : 4 = 7
28 × 5 = 140 (incincitul nr 28)
Verificare:
28 - 7 = 21
