Metoda mersului invers
163 - 15 = 148 calatori au ramas in tren, dupa ce au coborat jumatate
2 × 148 = 296 calatori erau in tren
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Notez numarul calatorilor cu ,, n "
n - n / 2 + 15 = 163 → ecuatie
2 n - n = 2 × ( 163 - 15 )
n = 2 × 148
n = 296 calatori erau in tren
Verific: 296 - 296 : 2 + 15 = 296 - 148 + 15 = 148 + 15 = 163