Stoichiometry

This Saturday I worked on an interesting stoichiometry problem:

How much coolant solution do I need to remove, if I want to replace the same volume of coolant with pure solute to arrive at a specified coolant concentration with the original volume.

It's solution involved simultaneous equations.

I found a plausible solution. Yay!

When I got to the lab today, and measured the actual concentration, it's about 1%. For the precision that I need I might as well just assume that the current concentration is zero and work from there. Simple arithmetic will do the job. As usual.