Question 1161215: Pure acid is to be added to a 10% acid solution to obtain 99L of a 20% acid solution
What amounts should be used ? Answer by ikleyn(52785) (Show Source):
Let x be the amount of the pure acid to add in order for to get 99L of a 20% solution.
It means that the amount of the 10% original acid was 99-x liters.
The equation to find x is THIS
0.1*(99-x) + x = 0.2*99. (1)
It says that the amount of the pure acid in ingredients (left side) is the same as in the mixture (right side).
Simplify and solve the equation
0.1*99 - 0.1x +x = 19.8
0.9x = 19.8 - 0.1*99
0.9x = 9.9
x = = 11.
ANSWER. 11 liters of the pure acid to add.
CHECK. I will check equation (1).
Ingredients: 0.1*(99-11) + 11 = 0.1*88 + 11 = 8.8+11 = 19.8 liters of the pure acid.
Mixture: 0.2*99 = 19.8 liters of the pure acid.
Both sides of the equation are equal. The check is completed.
Solved.
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It is a standard and typical mixture word problem.
