Two buses 210 km apart: 60 and 45 km/h

Two buses start 210 km apart and drive toward each other at 60 km/h and 45 km/h. After how many hours do they meet?

Step-by-step

1. 60 + 45 = 105
   Moving toward each other, the relative speed is the sum of the speeds
2. 210 ÷ 105 = 2
   Time to meet head-on = distance ÷ relative speed

Why it works

Driving toward each other, the two buses close the gap at the sum of their speeds, so the meeting time is the total distance divided by that sum.

Common mistakes

• Subtracting the speeds instead of adding them.
• Dividing 210 km by only one bus's speed.

Related

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