NIC Barber Written (Theory) ExamScientific ConceptsHard
A barber is preparing to clean and disinfect a reusable shaving razor. After thoroughly cleaning the razor with soap and water, the barber needs to immerse it in an EPA-registered disinfectant. If the disinfectant label states a 1:10 dilution ratio and the barber needs to prepare 1 gallon (128 fluid ounces) of solution, how much disinfectant concentrate is required?
- A12.8 fluid ounces
- B128 fluid ounces
- C10 fluid ounces
- D1.28 fluid ounces
Show answer & explanationAnswer & explanation
Correct answer: A. 12.8 fluid ounces
A 1:10 dilution ratio means 1 part concentrate to 10 parts water, making a total of 11 parts. However, in practical applications for disinfectants, a 1:10 ratio often implies 1 part concentrate to 9 parts water to make 10 total parts of solution. If 1 part concentrate is mixed with 9 parts water to make 10 total parts, then 1/10th of the total volume will be concentrate. So, 128 fluid ounces / 10 = 12.8 fluid ounces of concentrate.
Why the other options are wrong
- B. This implies no dilution (100% concentrate), which is incorrect and unsafe.
- C. This would be if the total solution was 100 fl oz, or if the ratio was 1:9 concentrate to total solution.
- D. This is a 1:100 dilution, which is too weak.
Disinfectant Dilution (1:10)
A common dilution ratio meaning 1 part concentrate is mixed with 9 parts water to create 10 total parts of solution.
- Total parts = 1 (concentrate) + 9 (water) = 10.
- Concentrate amount = Total Volume / 10.
- Always follow manufacturer's instructions.
- 1 gallon = 128 fluid ounces.
Memory trick: Divide by Ten for the Concentrated Gem.