In the video, the water level was $15$ milliliters before adding the chain, and $20$ milliliters after adding the chain. When I weighed the chain, its mass was $68\mathrm{.}2$ grams.

I believe the chain is solid metal $($not gold plated$),$ but is probably a blend of gold and other metals. I looked up that gold has a density of $19\mathrm{.}3\frac{g}{m}l,$ while the other metals like silver and copper usually blended with gold have a combined density of about $9\mathrm{.}7\frac{g}{m}l.$

Determine what percentage of the chain is gold, by mass, to at least $1$ decimal place?