Only if the entire mass is 18k gold. Not if the entire mass is 18k gold plus other Try your approach on two cases: 0% gold, with 100% unknown alloy, and 100% wa

Only if the entire mass is 18k gold. Not if the entire mass is 18k gold plus other Try your approach on two cases: 0% gold, with 100% unknown alloy, and 100% watch components. Like how foods made with "100% fruit" still have other ingredients.