|--------------------------------------------------------| → lungimea drumului
|-----|-----|-----|-----|-----|-----|-----|-----|-----|-----|
|-----|-----|-----| → prima zi
|-----|-----|-----|-----|-----|-----|-----|
|-----|-----| → a doua zi
|-----|-----|-----|-----|-----|
|-----|-----|-----| → a treia zi
|-----|-----| → 20 km. a patra zi
20 : 2 = 10 km
10 × 3 = 30 km ( a treia zi )
10 × 2 = 20 km ( a doua zi )
10 × 3 = 30 km ( prima zi )
20 + 30 + 20 + 30 = 50 + 50 = 100 km ( lungimea drumului )
Sper ca te-am ajutat !