The question was posed to me by my school principal while I was bunking the class.
The question is from Construction of Screw Threads topic in portion Curves used in Engineering Practice of Engineering Drawing
The best explanation: Pitch of the screw is 6 mm given screw is double-threaded so for one revolution the screw advances to 6 mm x 2 = 12 mm. But the screw advanced to 6 cm = 60 mm. Number of revolutions = total screw advancement/ screw advancement for single revolution = 60 /12 = 5.