First find the pot's volume in ml: 3 liters * 1000 ml/liter = <<3*1000=3000>>3000 ml
Then find the number of ml that enter the pot per minute: 3 drops/minute * 20 ml/drop = <<3*20=60>>60 ml/minute
Then divide the volume of the pot by the volume that enters it every minute: 3000 ml / 60 ml/minute = <<3000/60=50>>50 minutes
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