Two trains are moving in opposite directions at speeds of 60 km/h and 90 km/h. The distance between them is 300 km. After how much time will they meet?

Correct answer: 2 hour. Their relative speed is 60 + 90 = 150 km/h, so time = 300 ÷ 150 = 2 hours.

Background: When objects move toward each other, their speeds add.

• 1 hour: In 1 hour they would cover only 150 km.
• 3 hour: In 3 hours they would cover 450 km, more than 300 km.
• 4 hour: In 4 hours they would cover 600 km, more than 300 km.

Did you know? If they moved in the same direction, you would subtract the speeds.

Memory trick: Opposite → add speeds.