Loo roll emergency

When the roll of toilet paper is half as wide, what percentage of the paper is left?
Exploring and noticing Working systematically Conjecturing and generalising Visualising and representing Reasoning, convincing and proving
Being curious Being resourceful Being resilient Being collaborative

Problem



New toilet rolls are cylindrical, 12 cm in diameter, and the cardboard tube in the middle is 4 cm in diameter.
Image
Loo roll emergency


My roll has diameter 6 cm, so it looks about half the size.

What percentage of the toilet paper is left?