Notam:
X = lungimea drumului
prima zi:
X/5
a 2-a zi:
30/100(X - X/5) = 3/10(5X-X)/5 =3/10×4X/5 = 12X/50 = 6X/25
X/5 + 6X/25 + 56 = X |×25
5X + 6X + 1400 = 25X
25X- 11X = 1400
14X = 1400
X = 1400 : 14
X = 100 km (lungimea drumului)
Verificare:
100/5 + 6×100/25 + 56 =
= 20 + 24 + 56 = 100