You need a 15% alcohol solution. On hand, you have a 180 mL of a 45% alcohol mixture. How much pure water will you need to add to obtain the desired solution?
You will need
mL of pure water
to obtain
mL of the desired 15% solution.
Submit Question

Let x be the amount of pure water that you use.

The solution you have contains 0.45 • 180 mL = 81 mL of alcohol.

However much water you use, it won't add any alcohol to the solution, so only its total volume changes. Its new volume would be (180 + x) mL. You want the new solution to have a concentration of 15% so that

(81 mL) / ((180 + x) mL) = 0.15

Solve for x :

81 / (180 + x) = 0.15

81 / 0.15 = 180 + x

540 = 180 + x

x = 360

Then the new solution will have a total volume of 180 mL + 360 mL = 540 mL.

So you need to use 360 mL of pure water to get 540 mL of 15% solution.

is there a picture

step-by-step explanation:

answer: c, the green line

step-by-step explanation:

there is no black line, eliminate b.

simple interest implies periodic payments, but the red line shows no payments, eliminate d.

simple interest has equal payments. if paid say every day, the graph is about a straight line (actually a stairstep).

the yellow line is not straight, eliminate a.

check: the green line is straight, answer is c.

simple interest with positive interest rate gives a straight line sloping up to the right. green line:

g(t) = $100 + ($200-$100) ÷ (20 years) × (t years)

= $100 + (4%/year) × ($100)(t years)

incidentally, the yellow line curving upward represents continuously compounded interest

y = $100 × 2^(t years / (14 assuming the yellow line hits $200 at 14 years. 2^0 is 1, so y(0) = $100; 2^(14/14) is 2, so y(14) = $200.