To solve this problem, we can set up a proportion to find the amount of water needed to create the desired 80/20 mix.
Let's assume that x represents the amount of water (in gallons) that needs to be added.
We can set up the proportion as follows:
(10 gallons of water + x gallons of water) / (10 gallons of paint + x gallons of water) = 20% (or 0.2)
Simplifying the proportion, we get:
(10 + x) / (10 + x) = 0.2
To solve for x, we can cross-multiply:
0.2(10 + x) = 10 + x
2 + 0.2x = 10 + x
0.8x = 8
x = 10
Therefore, the correct answer is B) 1.25 gallons.