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Zach and Wang start running from the same place around a circular track of 500 meters in opposite direction.
The speed of Wang is 200 meters per minute, and they meet in one minute. What is Zach's speed in meters per minute?
If they run in the same direction at the very beginning, how many laps has Zach run when he catches up with Wang?
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Let's consider the first case when they run in opposite directions.
They meet, when the sum of the travel distances is equal to the track length of 500 meters
200*t + x*t = 500
where t= 1 minute is the time running and x is the Zach's running rate.
From the equation
x = = 300 meters per minute is the Zach's running rate.
Now, in the second scenario they run with their rates in one direction.
They meet, when the faster runner (Zach) will cover the distance, which is exactly one track' circumference longer than
the distance covered be the slower runner (Wang)
300*t - 200*t = 500.
From the equation, the time before Zach catches Wang is
t = = = 5 minutes.
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The problem is just solved --- all questions are answered.