# Pharmacy Mixture Calculations

by Andrea
(Tennessee)

30 grams of hydrocortisone 2.5% ointment is combined with 15 grams of hydrocortisone 1% ointment. What is the percentage of hydrocortisone in the final product?

### Comments for Pharmacy Mixture Calculations

 how to solve by: Brad Wojcik, Pharm D You have to know how many grams of HC and the total weight of the final product to calculate the final concentration. You have 30 g of 2.5% oint and 15 g of 1 % oint. You know you will end up with 45 g of final product by adding the 30 g and 15 g, that part is easy. In the 30 g of 2.5% you have 0.75g 30g oint(2.5g HC/100 g oint)= 0.75g and you have 0.15 g in the 15 g for a total of 0.9g HC. You end up with 0.9g HC/45 g oint, now change to a % by multiplying by 100%(0.9g HC/45g oint)(100%) = 2% w/wAnd yes, you multiply by 100%, not 100.

 unknown numbers by: Anonymous How did you get 0.75?

 answer by: Anonymous the 0.75 is the result of the (2.5/100)

 How did you get 0.15g? by: Anonymous How did you get 0.15g?

 Thats what I got by: Anonymous 0.15 came from: You have (15) grams of 1%1%= 1/100 = 0.01 = (15)*0.01 = 0.15

 I Found it simpler to just do it like this by: Anonymous [30g(2.5%)] + [15g(1%)] = 45g(x%) (75g%) + (15g%) = 45g(x%)90g% = 45g(x%)90g% = 45g(x%)---- ---45g 45g2% = x%