NIC Cosmetology Written (Theory) ExamScientific ConceptsHard
A cosmetologist is preparing to mix a disinfectant solution. The label states a 1:10 dilution ratio. If the mixing container holds 160 ounces, how much disinfectant concentrate is needed?
- A1.6 ounces
- B10 ounces
- C16 ounces
- D14.5 ounces
Show answer & explanationAnswer & explanation
Correct answer: C. 16 ounces
A 1:10 dilution ratio means 1 part concentrate to 10 parts water, making a total of 11 parts. However, in cosmetology, a 1:10 dilution often refers to 1 part concentrate to 9 parts water, meaning 1 part concentrate in a total of 10 parts solution. Therefore, to find the amount of concentrate, divide the total volume by the sum of the parts (1 + 9 = 10). So, 160 ounces / 10 = 16 ounces of concentrate.
Why the other options are wrong
- A. This would be a 1:100 ratio, or a miscalculation of the decimal place.
- B. This would be if the total solution was 10 parts and you needed 1 part concentrate, but the total volume is 160 ounces.
- D. This calculation would be incorrect for a 1:10 ratio in cosmetology context.
Dilution Ratio (1:X)
A common method for mixing disinfectants, where 1 part concentrate is mixed with X parts of water, creating a total of (1+X) parts solution OR 1 part concentrate in X total parts solution.
- In cosmetology, 1:10 usually means 1 part concentrate to 9 parts water, forming 10 total parts solution.
- Calculation: Total Volume / (1 + parts water) = Amount of Concentrate.
- Always follow manufacturer's instructions on the product label and SDS.
Memory trick: Diluting is 'Dividing' – 'Parts' make it 'Precise'!