Exam math · Treatment math
Percent strength and dilution
Relating chemical weight to solution weight, and diluting stock solutions to working strength.
The formula
Percent strength = weight of chemical over weight of solution, times 100. Dilutions: initial concentration times initial volume equals final concentration times final volume.
The unit trap
Percent problems become dosage problems the moment the exam converts percent to milligrams per liter: one percent is 10,000 mg/L. Memorize that bridge.
Worked practice example
Diluting a practice 10 percent stock to 0.5 percent: final volume is initial volume times 10 over 0.5, a twentyfold dilution. (Invented numbers.)
On exam day
A formula and conversion table is provided with the standardized exam; the official version is published by the exam provider at gowpi.org. These pages teach the concepts in our own words so the sheet on the desk reads as a reminder, not a puzzle.
The rest of the math
| Volumes | Tank volume |
| Volumes | Pipe and cylinder volume |
| Flow | Flow and velocity |
| Flow | Detention time |
| Treatment math | Chemical dosage |
| Treatment math | Removal efficiency |
| Hydraulics | Pressure and head |
| Hydraulics | Pump and horsepower math |
| Foundations | The conversion backbone |
| Foundations | Averages and loading rates |
| Foundations | The formula-first method |
The operator math sheet
One printable page: the exam format, the formula-first drill method, and the unit-conversion discipline that decides the math questions. Free.
No spam. One useful sheet and occasional notes.