|___________|___________|___________|___________|=> DRUMUL
\------------------/=>distanta de 4 ori mai mica decat drumul=>1/4 (din drum)
\--------------------------------------------------------/=>distanta ramasa
\-----------------/=>dist.de 3 ori mai mica=>1/3 (din rest)
\-------------------------------------/=>distanta ramasa
\-----------------/=>jumatate din rest=>1/2
\------------------/=>30 km.a patra zi
=>30 km a parcurs a patra zi
30*2=60 km ramasi in a treia zi
60:2=30 km parcutsi a treia zi
60+30=90 km ramasi a doua zi
90:3=30 km a parcurs a treia zi
90+30=120 km este lungimea drumului
120:4=30 km a parcurs in prima zi.
30+30+30+30=120 km in total