SOLUTION: You need 810 mL of a 30% alcohol solution. On hand, you have a 5% alcohol mixture and a 95% alcohol mixture. How much of each mixture will you need to obtain the desired solution?

Question 807978: You need 810 mL of a 30% alcohol solution. On hand, you have a 5% alcohol mixture and a 95% alcohol mixture. How much of each mixture will you need to obtain the desired solution?
How much of the 5% solution and how much of the 95% solution do I need?
Answer by josgarithmetic(39617) (Show Source): You can put this solution on YOUR website!
This same exercise problem occurs very frequently, shown in many different examples.

ASSIGN VARIABLES
L = 5% alcohol
T = 30%, the concentration target
H = 95%, the high concentration material
M = 810 mL, amount of T conc. wanted
u = unknown amount of L material
v = unknown amount of H material

FORMULATE EQUATIONS
and

SOLVE THE SYSTEM FOR u AND v.
You do the steps. The essential part (or maybe half of it) was to form the system of equations. The steps after that are routine.
RELATED QUESTIONS
You need 1425 mL of a 30% alcohol solution. On hand, you have a 5% alcohol mixture. How... (answered by josgarithmetic)

You need 210 mL of a 90% alcohol solution. On hand, you have a 25% alcohol mixture and a... (answered by mananth)

You need 1275 mL of a 15% alcohol solution. On hand, you have a 10% alcohol mixture and a (answered by TimothyLamb)

You need a 30% alcohol solution. On hand, you have a 440 mL of a 5% alcohol mixture. You... (answered by josgarithmetic)

You need a 90% alcohol solution. On hand, you have a 60 mL of a 20% alcohol mixture. You... (answered by nerdybill)

You need a 80% alcohol solution. On hand, you have a 225 mL of a 15% alcohol mixture. You (answered by josmiceli,mananth)

You need 1235 mL of a 85% alcohol solution. On hand, you have a 5% alcohol mixture. How... (answered by addingup)

You need 1040 mL of a 20% alcohol solution. On hand, you have a 15% alcohol mixture. You... (answered by josgarithmetic,greenestamps,math_tutor2020)

You need 240 mL of a 45% alcohol solution. On hand you have a 30 % alcohol mixture and a... (answered by richwmiller)