How much water do I add to 128 ounces of a 10% solution to reduce it to a 2% solution?

Answer 1

128*0.10 = x*0.02 where x is going to be the final volume
x=640
you already have 128, so add 512

Answer 2

Let x = amount of water you need to add, so 128+x = total weight of final 2% solution:

(128 ounces x 10% solution) / (128 ounces + x) = 2%

so x = 512 ounces.

It's unusual that you stated the weight of the solution. Usually, the volume of the solution is the unit of preference.

Answer 3

To reduce the concentration by a factor of 5 you must increase the volume by a factor of 5. So the water you add must be 4x the original volume, so that the final volume is 5x the original volume.

Answer 4

The first two answers are very good.