Calculating the Amount of a Specific Item
In this section you will find out how to calculate the actual amount of a specific item, given the percentage of the item and the total amount present.
There are 75 g of an ointment, and 1 % of the ointment by mass is drug A. What is the mass of drug A in the 75 g of ointment?
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There are 0.75 g of drug A in 75 g of the ointment.
Remember,
100
Amount of Drug A = 0.75 g
Remember,
percentage = actual amount of item x 100 %
total amount all items
and this rearranges to give:total amount all items
Actual amount of item = percentage x total amount present
100
So, Amount of Drug A = 1 x 75 g100
100
Amount of Drug A = 0.75 g