Hikers 3200 m apart: 85 and 75 m/min

Two hikers start 3200 m apart and walk toward each other at 85 m/min and 75 m/min. After how many minutes do they meet?

Step-by-step

1. 85 + 75 = 160
   Moving toward each other, the relative speed is the sum of the speeds
2. 3200 ÷ 160 = 20
   Time to meet head-on = distance ÷ relative speed

Why it works

Walking toward each other, the two hikers close the distance 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 3200 m by only one hiker's speed.

Related

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