A certain quantity of 40% concentration solution is replaced with 25% ...
After the replacement, the concentration of the combined solution becomes 35%. We can use the concept of weighted averages to solve this problem.
The initial solution of 40% concentration is being replaced with a 25% concentration solution. The resulting concentration of the combined solution is 35%. This means that the 40% solution is being diluted.
To find the ratio of the amounts, we can set up the following equation based on the concentrations and quantities:
(40% * x) + (25% * y) = 35% * (x + y)
where "y" represents the amount of the 25% concentration solution that was added.
Simplifying the equation:
(0.4x) + (0.25y) = 0.35x + 0.35y
0.25y - 0.35y = 0.35x - 0.4x
-0.1y = -0.05x
y/x = 0.05/0.1
y/x = 1/2
From the equation, we can see that the ratio of the amount of solution that was replaced (y) to the amount of solution that was not replaced (x) is 1:2.
Therefore, the correct answer is B: 1:2.