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Question:

What is the weight/weight percent (w/w%) of 412.5 mg of nitroglycerin in 33 grams of a compounded prescription?

A 1.25% nitroglycerin
Explaination

Weight/weight (w/w%)—measured in grams of the ingredient/100 grams of the total product: 412.5 mg = 0.4125 grams (There are 1,000 mg in one gram—just move decimal 3 places to the left.) 0.4125 grams/33 grams = 0.0125 = 1.25% (To get a %, multiply by 100—or move the decimal 2 places to the right.)