Cyclists 1200 m apart: 250 and 150 m/min

Two cyclists start 1200 m apart and ride toward each other at 250 m/min and 150 m/min. After how many minutes do they meet?

Step-by-step

1. 250 + 150 = 400
   Moving toward each other, the relative speed is the sum of the speeds
2. 1200 ÷ 400 = 3
   Time to meet head-on = distance ÷ relative speed

Why it works

Riding toward each other, the two cyclists 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 as if one were chasing the other.
• Using only one cyclist's speed to divide 1200 m.

Related

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