If a pharmacist added 12 g of azelaic acid to 50g of an oint

If a pharmacist added 12 g of azelaic acid to 50g of an ointment containing 15% azelaic acid, What would be the final concentration of azeliac acid in the ointment.

Answer is 31.5% Please show steps

Solution

HEre total mixture = 50+12= 62 g

Now 15% of 50 = 0.15 x 50 = 7.5g

So total grams of azelaic acid in last mixture = 12+ 7.5 = 19.5 g

And let x% of 62 = 19.5

or 62x/100 = 19.5

or 62x = 19.5(100 ) = 1950

or x= 1950/62 = 31.5%

This is how we get our answer.