Two trains, 300 m and 90 m long, are running on parallel tracks in opposite directions at 90 km/h and 18 km/h. How long will they take to cross each other completely?

💡 Solution & Explanation

In opposite directions, the speeds add: 90 + 18 = 108 km/h = 108 × 5/18 = 30 m/s. To cross completely, they cover both lengths: 300 + 90 = 390 m. Time = 390 ÷ 30 = 13 seconds. In the same direction the speeds would subtract instead.