W/W Percentage Equation

Question

An ointment is prepared by incorporating $10\,\mathrm{g}$ of a drug into a $100\,\mathrm{g}$ of white petrolatum. What is the percent w/w of active ingredient?

The answer is $9.1\,\%$. I don't know how it came up with the answer because I always get $10\,\%$. Thank you for answering!

How much ointment do you have when it is made? – user121049 Jun 09 '17 at 12:21 — user121049, Jun 09 '17 at 12:21

score 1 · Answer 1 · edited Jun 09 '17 at 13:02

1

You have $10\,\mathrm{g}$ of a drug and $100\,\mathrm{g}$ of white petrolatum, so $110\,\mathrm{g}$ in total.

So, you have $$\frac{10}{110} \cdot 100\,\% = 9.1\,\%$$ of a drug.

edited Jun 09 '17 at 13:02

Björn Friedrich

3,747

answered Jun 09 '17 at 12:31

Andrei Rykhalski

1,325
9
14

W/W Percentage Equation

1 Answers1