Does anyone have the formula to figure the amount of pure silver

needed to raise the fineness of coin silver or lower to sterling

silver. I have some .625 fine Olympic coins that I want to raise to

.925. I know that 1 oz of .625 silver should have approximately 12.5

dwt ( 19.4375 grams ) of fine silver and 7.5 dwt ( 11.6625 grams ) of

alloy so to raise 1 oz of.625 to .925 I should need 4 ozs of pure

which would give me 92.5 dwt of silver and 7.5 dwt of alloy but there

must be an easy mathematical formula to use.

Thanks

Greg DeMark

http://www.natureinspiredjewelry.com