The alloy contains half as much gold as silver How many parts of gold are there in one part of silver?

By the condition of the problem, we know that the alloy contains half as much gold as silver. This means that in the alloy there are 2 parts of silver for one part of gold. In order to determine how many parts of gold are in one part of silver, we will reduce this ratio of parts in the alloy by 2:

1 part gold / 2 = 0.5 parts gold.

Conclusion: for one part of silver, to make an alloy, you need to take 0.5 parts of gold.