Răspuns:
Explicație pas cu pas:
AB = 45 cm
AM/3 = MN/5 = NB/7
AM+MN+NB = 45
AM = 3MN/5 ; NB = 7MN/5
3MN/5 + ⁵⁾MN + 7MN/5 = ⁵⁾45
3MN + 5MN + 7MN = 225
15MN = 225 => MN = 225:15 => MN = 15 cm
AM = 3·15:5 = 3·3 => AM = 9 cm
NB = 7·15:5 = 7·3 => NB = 21 cm
15+9+21 = 15+30 = 45 cm