gfn shows the range of the sand size. as we know sand are differ in shapes and sizes. if the gfn is between 40 and 100 it can be classified as coarse and 100-220 is fine. typically for ferrous...
To calculate that answer to "a is what percentage of b" divide a by b, then move the decimal point two places to the right.In more rigorous terms: divide a by b, then multiply by 100. But the answer...