Question 1182444
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the track is a 500m circuit. Ali practices running at a speed of 10kph. 
Ben practices cycling and travels at 25kph. How long does Ali take to run one lap?
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Calculations in the post by @CPhill are incorrect.


He lost the necessary precision and came to wrong answer of 185 seconds.


The correct answer is 180 seconds, or 3 minutes,

as it is shown in correct solutions by @greenestamps and @ikleyn at this spot.


The error in 5 seconds is CATASTROFICAL for this problem.



I recommend to a reader to ignore the post by @CPhill.