[tex]l = lungimea \: drumului \\ 82 + \frac{1}{2} \times (l - 82) + \frac{2}{5} \times l \\ 82 + \frac{1}{2} \times 1 - \frac{1}{2} \times 82 + \frac{2}{5} \times l \\ 82 + 0.5 \times l + 41 + 0.4 \times l \\ 41 + 0.9 \times l \\ 0.1 = 41 \\ l = 410[/tex]
