- Notăm distanța totală cu d.
Prima zi:
[tex]30\% \: din \: d = \frac{30d}{100} = \frac{3d}{10} [/tex]
A doua zi:
[tex] \frac{1}{2} \times (d - \frac{3d}{10} ) = \frac{1}{2} \times \frac{7d}{10} = \frac{7d}{20} [/tex]
A treia zi: 90 km
[tex] \frac{3d}{10} + \frac{7d}{20} + 90 = d < = > \frac{6d}{20} + \frac{7d}{20} + \frac{1800}{20} = \frac{20d}{20} \\ (amplificam \: cu \: 20 \: ca \: sa \: eliminam \: numitorii) \\ 6d + 7d + 1800 = 20d < = > 20d - 6d - 7d = 1800 < = > 7d = 1800 = > d = \frac{1800}{7} aprox = 257.14 \: (km)[/tex]
