Problema Solution
A pharmacist needs to obtain a 70% alcohol solution. How many ounces of a 30% alcohol solution must be mixed with 40 ounces of an 80% alcohol solution to obtain a 70% alcohol solution?
Answer provided by our tutors
concentration = pure alcohol / total volume
we have 40 oz of 80% solution, which means we have this much pure alcohol:
40 * 0.8 = 32
we want a 70% solution, so we add 'v' ounces of a 30%:
0.70 = (32+0.3v)/(40+v)
solving for 'v' we have v=10
the pharmacist should add 10 ounces of the 30% solution