Final answer:
The fraction of yellow paint used for every 1 part blue paint is 2/3.
Step-by-step explanation:
To find the fraction of yellow paint used for every 1 part blue paint, we need to first convert the given ratio into fractions.
Given: 2/3 part blue for every 2/5 part yellow
This means that for every 2 parts yellow, there are 3 parts blue. So, the ratio can be written as 2/5 yellow for every 3/5 blue. We can simplify this to 2/5 yellow for every 3/5 blue. Therefore, the fraction of yellow paint used for every 1 part blue paint is 2/3.