Question 1060519
let x be the number of liters for the 10% solution
let y be the number of liters for the 25% solution
:
total liters for 10% solution is 0.10x
total liters for 25% solution is 0.25y
:
x + y = 30
total liters of 15% solution is 0.15 * 30 = 4.50 liters
:
y = 30 - x
:
0.10x + 0.25(30-x) = 4.50
:
Note that I substituted for y for the 25% solution
:
0.10x + 7.50 -0.25x = 4.50
:
-0.15x = -3.00
:
x = 20
:
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The chemist used 20 liters of the 10% solution
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