SOLUTION: Rx: zink oxide 20% ointment 90g. how many grams of zink oxide 40% ointment and zink oxide 10% ointment should you mix to prepare the prescription.

Question 629214: Rx: zink oxide 20% ointment 90g. how many grams of zink oxide 40% ointment and zink oxide 10% ointment should you mix to prepare the prescription.
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = grams of 40% ointment needed
Let = grams of 10% ointment needed
given:
(1)
(2)
-------------------------
(2)
(2)
(2)
Subtract (1) from (2)
(2)
(1)

and, since
(1)
(1)
(1)
30 grams of 40% ointment are needed
60 grams of 10% ointment are needed
check:
(2)
(2)
(2)
(2)
OK
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