Walkers 2400 m apart: meeting time

Two people start 2400 m apart and walk toward each other at 90 m/min and 60 m/min. After how many minutes do they meet?

Step-by-step

1. 90 + 60 = 150
   Moving toward each other, the relative speed is the sum of the speeds
2. 2400 ÷ 150 = 16
   Time to meet head-on = distance ÷ relative speed

Why it works

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

Common mistakes

• Using the difference of the two speeds.
• Forgetting to add the two speeds before dividing.

Related

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