Question

Marie mixes 20 liters of 12% acid solution with a 36% acid solution to make a 20% acid solution. How many liters of 36% solution did she use? 10 liters 12 liters 13.7 liters 16 liters

Answer 1

Answer: First Option

10 liters

Step-by-step explanation:

Let's call x the quantity in liters of the acid solution at 12%

Let's call z the amount in liters of the acid solution at 36%

Then the amount of acid in the solution will be:

$0.12x + 0.36z = (x + z) * 0.2$

We know that x = 20 liters, then we substitute x = 20 in the equation solve the equation for z

$0.12 (20) + 0.36z = (20 + z) * 0.2$

$2.4 + 0.36z = 4 + 0.2z\\\\0.16z = 4-2.4\\\\0.16z = 1.6$

$z = 10$