F = T - 25
T : F = 6 => T = 6×F
F = 6 × F - 25
6×F - F = 25
5×F = 25
F = 25 : 5
F = 5 ani (fiul)
T = 6×5 = 30 ani (tatal)
o alta metoda de rezolvare:
T - F = 25
T = 6×F
T |___|___|___|___|___|___|
F |___|
6 segmente egale - 1 segment egal = 5 segmente egale = 25
25 : 5 = 5 (un segment egal)
T = 6×5 = 30 ani
F = 5
Verificare:
5 = 30 -25
5 = 5
30 : 5 = 6