(4) Mixed Types of Percentage problems
3. Percent, Ratio, mg/mL, PPM, PPB 3.1) Percent 3.1.1) Percent - General
3.1.1.1) Percent from weight and volume Easy 1
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How many milligrams of drug do you need to prepare 405 mL of a vaginal douche, so that the strenght becomes 1.65 % `w/v`?
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lb equals 6682.5 mg kg
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Percentage (w/v) means number of grams of drug present per 100 mL of the solution. Here, the strength is 1.65 %, which means, there is 1.65 g of drug dissolved per 100 mL of a vaginal douche. We need to determine the weight (in mg) of drug present in 405 mL of it.
`∴ (1.65 \quad g)/(100 \quad mL) = x/(405 \quad mL) ⇒ x = 6.6825 \quad g`
1 g equals 1000 mg.
∴ there will be `6.6825 g × (1000 mg)/(1 g) = 6682.5` mg drug present. (Ans).