SOLUTION: Science and medicine. A pharmacist wishes to prepare 150 mL of a 20% alcohol solution. She has a 30% solution and a 15% solution in her stock. How much of each should be used in f

Question 74968: Science and medicine. A pharmacist wishes to prepare 150 mL of a 20% alcohol
solution. She has a 30% solution and a 15% solution in her stock. How much of each should be used in forming the desired mixture?

Answer by psbhowmick(878) (Show Source): You can put this solution on YOUR website!
Let us suppose that 'x' ml of 30% alcohol be mixed with 'y' ml of 15% alcohol to form 150 ml of 20% alcohol.

150 ml of 20% alcohol consists = 30 ml of alcohol and (150 - 30) = 120 ml of water.

Similarly, 'x' ml of 30% alcohol contains = 0.3x ml and (x - 0.3x) = 0.7x ml of water.
Also, 'y' ml of 30% alcohol contains = 0.15y ml and (y - 0.15y) = 0.85y ml of water.

Thus total volume of alcohol in final mixture = (0.3x + 0.15y) ml and total volume of water in final mixture = (0.7x + 0.85y) ml.

But final mixture contains 30 ml alcohol and 120 ml water.

So, ______________(1)
and ______________(2)

Multiplying (1) by 7 and (2) by 3 and subtracting (1) from (2)

So, [from (1)]

Hence, 50 ml of 30% alcohol should be mixed with 100 ml of 15% alcohol.
RELATED QUESTIONS
a pharmacist wishes to prepare 30ml 0f a 20% alcohol solution. She has 30% solution and... (answered by robertb)

a pharmacist wishes to prepare 36mL of 20% alcohol solution. she has 30% solution and 10% (answered by richwmiller)

A pharmacist has 10% and 30% alcohol solutions in stock. To prepare 200 mL of a 25%... (answered by Alan3354)

A pharmacist wants to prepare 300 ml of a 20 percent alcohol solution. How much of a 30... (answered by josgarithmetic,josmiceli,MathTherapy)

A pharmacist has a 10% alcohol solution and a 25% alcohol solution. How many milliliters... (answered by Alan3354)

If a pharmacist wants to make 150 milliliters of a 20 percent alcohol solution, but only... (answered by oberobic,josmiceli)

a pharmacist has 10% and 30% alcohol solutions instock. to prepare 200mL of 25% solution... (answered by josmiceli)

a pharmacist wishes to mix a solution that is 2% Minoxidil. She has on hand 80 ml of a 1% (answered by nerdybill)

A pharmacist wishes to mix a solution that is 6% Minoxidil. She has on hand 80 ml of a... (answered by jorel555)