Answer:
98.57 L
Step-by-step explanation:
We can use the relation that
Volume of paint × concentration of pigment = amount of pigment
or
V × c = P
If we call the three solutions 1, 2, and 3, then
P₁ + P₂ = P₃
V₁c₁ + V₂c₂ = V₃c₃
Let x = the volume of 11 % paint.
Then
230 × 21 % + x × 11 % = (230 +x) × 18 %
4830 + 11x = 4140 + 18x Subtract 4140 from each side
690 + 11x = 18x Subtract 11x from each side
690 = 7x Divide each side by 7
x = 98.57 L
The employee should add 98.57 L of the 21 % pigment paint.
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Check:
230×21 + 11×98.57 = (230+98.57)×18
4830 + 1084 = 328.57×18
5914 = 5914