The film was wound on the disc, the diameter of the disc center of the empty disc was 60mm, and the existing film with the thickness of 0. 15mm was tightly wound on the disc for 600 times. Q: What is

The film was wound on the disc, the diameter of the disc center of the empty disc was 60mm, and the existing film with the thickness of 0. 15mm was tightly wound on the disc for 600 times. Q: What is the quality of this film? C=∏d

C film = ∏ (60+0.3)+∏ (60+0.3+0.3)+...+∏ (60+600 * 0.3)

=∏60*600+0.3( 1+2+3+……+600)

=90090∏

It is approximately equal to 3. 14.

C membrane = 282882.6mm = 28.28826m m.

That is, the film is about 28 meters long.