Which situation represents inverse proportion?

Which situation represents inverse proportion?
  1. Number of pens bought and total cost
  2. Number of workers and time to finish a fixed job
  3. Side of a square and its perimeter
  4. Distance travelled and time at fixed speed

Solution

More workers means less time for a fixed amount of work; (workers) $\times$ (time) is constant. Inverse.

Asked in: IMO

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