NIC Cosmetology Written (Theory) ExamScientific ConceptsHard
A cosmetologist is preparing a disinfectant solution for general use in the salon. The disinfectant product label states a dilution ratio of 1:128. If the cosmetologist needs to prepare 2 gallons of solution, how much disinfectant concentrate should be used? (Note: 1 gallon = 128 fluid ounces)
- A1 fluid ounce
- B0.5 fluid ounces
- C2 fluid ounces
- D4 fluid ounces
Show answer & explanationAnswer & explanation
Correct answer: C. 2 fluid ounces
A 1:128 dilution means 1 part concentrate to 128 parts water (or total solution). For 2 gallons (2 * 128 = 256 fluid ounces) of solution, you divide the total fluid ounces by the dilution ratio: 256 fluid ounces / 128 = 2 fluid ounces of concentrate.
Why the other options are wrong
- A. This would be for 1 gallon of solution at a 1:128 ratio.
- B. This would be for 1 gallon if the ratio was 1:256, or half a gallon at 1:128.
- D. This would be for 4 gallons at 1:128 or 2 gallons at 1:64.
Dilution Ratio (1:X)
Indicates the proportion of concentrate to the total solution. For 1:X, it means 1 part concentrate to X parts total solution (or X-1 parts water).
- 1:X means 1 part concentrate to X parts total solution
- Used to prepare proper strength disinfectants
- Always follow manufacturer's instructions
Memory trick: Total Volume Divided by Ratio equals Concentrate to Contain.