Final answer:
The total number of parts in the alloy with a nickel, zinc, and copper ratio of 2:7:9 is found by summing the parts of each metal, resulting in a total of 18 parts.
Step-by-step explanation:
The total number of parts in the alloy made of nickel, zinc, and copper can be calculated by adding the ratio numbers given for each metal. The ratio provided is 2:7:9 which means for every 2 parts of nickel, there are 7 parts of zinc and 9 parts of copper.
Here is the step-by-step calculation:
Add the parts of nickel, zinc, and copper: 2 (nickel) + 7 (zinc) + 9 (copper) = 18 (total parts).
Therefore, the total number of parts in the alloy is 18.