The radius of the cylinder is = 9
The ends of the rollers are surrounded by metal strip. The metal strip goes round the circle. That is the circumference of the circle.
C = 2πr = 2π9 = 18π cm.
Length of metal sheet on one of the circle = 18π cm.
For the 3 rollers = 18π 3 = 54π cm. Using π ≈ 3.14
Length = 54π ≈ 54*3.14 ≈ 169.56 cm
Therefore length for the 3 metal strips = 54π ≈ 169.56 cm