by Guest » Wed Aug 19, 2015 12:35 pm
If 3 is the answer you want, then that is a trivial solution... ie 5 - 2 = 3. and you don't need to know the grooves are 90 per inch
I thought the question was asking how far does the needle around the surface of the disk as it rotated to play the recording... ie the length of the recording, which is 495 feet.