Our local cricket team has just bought a new roller, and a very impressive bit of equipment it is too. Although having seen its unusual feature we are not convinced of its benefits; no doubt the marketing material extolled its virtues.
The roller has a large hollow cylinder with an outside circumference of 60 inches and an inside circumference of 50 inches. And the clever feature we referred to earlier - it has another, this time solid, cylinder inside the hollow cylinder. This one is 24 inches in circumference.
The solid cylinder rests on the inside of the hollow cylinder and rotates as the roller is pushed. Apparently this arrangement makes it easier to stop the roller without overshooting.
The roller is pushed exactly 60 feet when rolling the pitch. So how many times does the small cylinder rotate during this 60-foot journey?
To cover the 60 feet of cricket pitch the roller, and thus the large cylinder, will rotate twelve times. Twelve revolutions of the inside of the hollow cylinder is (12 x 50) 600 inches. So the small cylinder will rotate (600 / 24) 25 times.