Name: Sandy

Who is asking: Teacher
Level: All

A colleague and I have a disagreement about dilutions. I seem to remember that I was taught (although it was a long time ago) that a RATIO was written thusly: 1:5 , and read " one part to five parts", for a total of 6 parts. On the other hand, a fraction is written: 1/5 and is read" one part in five" for a total of 5 parts. My colleague says that the ratio reads "one part in five" and is essentially the same as a fraction. Which is right? Have I been doing dilutions wrong all this time? I teach Animal Nursing and need to know where I can find a consise answer to such questions for making up medicated fluids, etc. Thank you.

Hi Sandy,

You are correct. If you make salad dressing with vinegar and oil in the ratio of 1:5, then you put in 1 ml of vinegar and 5 ml of oil to get 6 ml of salad dressing. The resulting dressing is composed of one-sixth vinegar and five-sixths oil. I would read the "1:5" notation by saying that the dressing has vinegar and oil in the ratio of one to five.

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