Answer:
12 g of silver
Explanation:
5 rings and each weighs 16 g. Hence, the total mass of the 5 rings is: 5 x 16 = 80 g
Each ring contains 5% silver and 95% gold. hence:
Silver content of the 5 rings = 5/100 x 80 = 4 g
Gold content of the 5 rings = 80 - 4 = 76 g
In order to reduce the gold content of the 80 g melted ring to 80%, the silver must be increased to 20%;
5% silver is equivalent to 4 g
20% silver = 4 x 20/5 = 16 g
Since 4 g of silver is originally present in the melted mixture and 16 g of silver is required, then 12 g of silver needs to be added.