Answer:
Part A: A ratio of 2:1 means that he uses 2 cups of yellow paint for each cup of blue paint.
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Part B: The ratio of yellow to blue is 2:1 = 2/1. So, if for 2 yellow is 1 blue, then for 1 yellow is x:
2/1 = 1/x
x = (1*1) / 2
x = 1/2
For each cup of yellow paint, Greg should add 1/2 cup of blue paint.
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Part C: 6 cups cost $54, then 1 cup cost:
54 / 6 = 9
The price per cup of yellow paint is $9.