16. A roll of adhesive tape is wound round a central cylindrical core of radius 3cm. The outer radius of a roll containing 20m or tape is 4cm. Approximately what is the outer radius of a roll containing 80m of tape?
16. A roll of adhesive tape is wound round a central cylindrical core of radius 3cm. The outer radius of a roll containing 20m or tape is 4cm. Approximately what is the outer radius of a roll containing 80m of tape?
A5cmB5.5cmC6cmD7cmE12cm
5.5 right?
The 20m tape is wound round so that the total area of the wound disk is 5pi cm^2. The ratio of 20m to 5pi must be the same for the area of the larger disk and the 80m.
16. A roll of adhesive tape is wound round a central cylindrical core of radius 3cm. The outer radius of a roll containing 20m or tape is 4cm. Approximately what is the outer radius of a roll containing 80m of tape?
A5cmB5.5cmC6cmD7cmE12cm
I got 7...... (But I *usually* trust james so go with him answer!)
The 20m tape is wound round so that the total area of the wound disk is 5pi cm^2. The ratio of 20m to 5pi must be the same for the area of the larger disk and the 80m.
I think the approach is correct, but i get 6 as an answer :