Question

How many liters of water should be added to 18 liters of a 14% bleach solution so that the resulting solution contains only 10% bleach? original (l) added (l) new (l) amount of bleach 2.52 0 amount of solution 18 x 1.8 liters 7.2 liters 15.5 liters 25.2 liters

Answer 1

18 liters of 14% bleach contains 0.14×18 = 2.52 liters of bleach.

Adding $x$ liters of pure water to the solution increases the total volume to $18+x$ liters without changing the total amount of bleach.

To end up with a 10% bleach solution, we must add

$\dfrac{2.52}{18+x} = 0.10 \implies 2.52 = 1.8 + 0.10x \implies 0.10x = 0.72 \implies x=\boxed{7.2}$

liters of water.