Final answer:
When adding 10 ounces of pure gold to 60 ounces of an alloy to make 70 ounces total, and assuming all the initial alloy is gold, the new percentage of gold in the alloy would be 100%.
Step-by-step explanation:
To calculate the percentage of gold in the alloy after Jess adds 10 more ounces of pure gold, we need to consider both the new amount of gold and the total weight of the alloy. Prior to adding the gold, we don't have information about the percentage of gold in the initial 60 ounces of alloy. However, after adding 10 ounces, we assume the total weight of the alloy is now 70 ounces.
If we add 10 ounces of pure gold to 60 ounces of an alloy, we then have a total of 70 ounces of substance. Of these, 10 ounces are pure gold, but we are not given information about how much of the 60 ounces of the initial alloy is gold; assuming all of it is gold for the purpose of this calculation, the new percentage of gold would be:
Percentage of gold = (Weight of gold) / (Total weight of alloy) * 100%
Percentage of gold = (60 oz + 10 oz) / 70 oz * 100%
Percentage of gold = 70 oz / 70 oz * 100%
Percentage of gold = 100%
Therefore, the answer to the question is C) 100% if all the original alloy was gold, and that's what we've assumed in this calculation.