metoda mersului invers
x - lungimea traseului
I. x/2+4 km; II. (x/2+4 km):2; III. 4 km
(4 km+4 km)×2=16 km
(16+4)×2=20×2=40 km
(40+4)×2=88 km lungimea traseului
prin ecuatie:
x=traseul
x/2+4=ziua1
x-(x/2+4)=x/2-4=rest
(x/2-4)×1/2+4=x/4-2+4=x/4+2=ziua2
x/2-4-(x/4+2)=x/2-4-x/4-2=x/4-6=rest
(x/4-6)×1/2+4=x/8-3+4=x/8+1=ziua 3
x/2+4+x/4+2+x/8+1+4=x
x/2+x/4+x/8+11=x
4x+2x+x+88=8x
x=88 km