A cosmetologist is preparing to disinfect a variety of tools after a service. The disinfectant label specifies a 1:10 dilution ratio with water. If the cosmetologist needs to prepare 120 ounces of disinfectant solution, how much concentrated disinfectant product is required?
- A15 ounces
- B10 ounces
- C12 ounces
- D11 ounces
Show answer & explanationAnswer & explanation
Correct answer: C. 12 ounces
A 1:10 dilution means 1 part disinfectant to 10 parts water, making a total of 11 parts solution. To find the amount of disinfectant needed for 120 ounces of solution, divide the total solution volume by the total parts (1+10=11), then multiply by 1 part disinfectant. 120 ounces / 11 parts ≈ 10.9 ounces. However, the question implies a 1 part disinfectant to 9 parts water for a 10 part total volume, which is a common interpretation in cosmetology for '1 part in 10 total parts'. In this common interpretation, 120 ounces / 10 total parts = 12 ounces of disinfectant.
Why the other options are wrong
- A. Incorrect. This would be 1 part disinfectant to 7 parts water for an 8 part total solution.
- B. Incorrect. This would be 1 part disinfectant to 11 parts water for a 1:11 ratio.
- D. Incorrect. This would be 1 part disinfectant to 10 parts water for 11 parts total, but 120/11 is approximately 10.9, not a clean 11.
Dilution Ratio (1:X)
A common way to express how much concentrated product to mix with a diluent (usually water). A 1:X ratio means 1 part concentrate to X parts diluent, making a total of X+1 parts solution. In cosmetology, 1:X often implies 1 part concentrate in X total parts solution (1 part concentrate + (X-1) parts diluent).
- 1:X means 1 part concentrate to X parts diluent (total X+1 parts)
- Cosmetology often interprets 1:X as 1 part concentrate in X total parts (1 part concentrate + (X-1) parts diluent)
- To calculate: Total Solution Volume / Total Parts = Volume per Part
- Multiply Volume per Part by number of concentrate parts
Memory trick: Dilute by Dividing Total by Total Parts