Quote:
Originally posted by Wdnesday
The outer track of a phonograph record is a circle of radius 6 inches. The undused center of the disk is a circle of radius 3 inches. If the record has 20 grooves per inch, how far, to the nearest inch, does the needle travel white the record plays from beginning to end? |
EDIT : did it wrong the first time
Average radius = 4.475 (middle of two inside tracks)
Total grooves = 60
Total radius = 8.95 * 30 (each pair of inside and outside grooves add up to a radius of 8.95) = 268.5
Total distance = 2 * 268.5 * pi (use 3.14)
= 1681 inches
Still can't believe I'm doing maths on uni holidays...
