The unknown quantity of kilograms of water that must be added to obtain a 5% solution is determined by the conditional variable “Y”.
Based on the conditions of the problem, we get the following equation: (40 x 10/100) / (40 + Y) = 5/100.
The outcome of the calculation looks like this (40/10) / (40 + Y) = 1/20 or 4 / (40 + Y) = 1/20 or 4 x 20 = 40 + Y or Y = 80 – 40 = 40 kilograms water.
Answer: add 40 kilograms of water to the solution.
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