Solved on Jan 20, 2024

Determine the amount of 100%100\% antifreeze needed to replace the 20%20\% solution in a radiator to achieve a 40%40\% antifreeze solution.

STEP 1

Assumptions
1. The radiator currently contains 70 liters of a 20% antifreeze solution.
2. We want to achieve a 40% antifreeze solution in the radiator.
3. We will drain a certain amount of the 20% solution and replace it with 100% antifreeze to reach the desired concentration.
4. The total volume of the solution in the radiator remains 70 liters after the process.

STEP 2

Let's denote the amount of solution to be drained and replaced with 100% antifreeze as xx liters.

STEP 3

The amount of antifreeze in the original 20% solution is 0.20×700.20 \times 70 liters.
Antifreezeoriginal=0.20×70Antifreeze_{original} = 0.20 \times 70

STEP 4

Calculate the amount of antifreeze in the original solution.
Antifreezeoriginal=0.20×70=14 litersAntifreeze_{original} = 0.20 \times 70 = 14\ \text{liters}

STEP 5

When xx liters of the 20% solution are drained, we lose 0.20×x0.20 \times x liters of antifreeze.

STEP 6

After draining xx liters of the 20% solution, the remaining antifreeze in the radiator is 140.20×x14 - 0.20 \times x liters.

STEP 7

We then add xx liters of 100% antifreeze to the radiator.

STEP 8

The total amount of antifreeze in the radiator after adding xx liters of 100% antifreeze is (140.20×x)+x(14 - 0.20 \times x) + x liters.

STEP 9

We want the final solution to be 40% antifreeze in a 70-liter solution.
Antifreezefinal=0.40×70Antifreeze_{final} = 0.40 \times 70

STEP 10

Calculate the amount of antifreeze needed in the final solution.
Antifreezefinal=0.40×70=28 litersAntifreeze_{final} = 0.40 \times 70 = 28\ \text{liters}

STEP 11

Set up the equation to find xx by equating the antifreeze in the final solution to the total amount of antifreeze after the replacement.
(140.20×x)+x=28(14 - 0.20 \times x) + x = 28

STEP 12

Simplify the equation by combining like terms.
140.20x+x=2814 - 0.20x + x = 28
14+0.80x=2814 + 0.80x = 28

STEP 13

Subtract 14 from both sides of the equation to isolate the terms with xx.
0.80x=28140.80x = 28 - 14
0.80x=140.80x = 14

STEP 14

Divide both sides of the equation by 0.80 to solve for xx.
x=140.80x = \frac{14}{0.80}

STEP 15

Calculate the value of xx.
x=140.80=17.5x = \frac{14}{0.80} = 17.5

STEP 16

The amount of the 20% antifreeze solution that needs to be drained and replaced with 100% antifreeze to obtain a 40% solution in the radiator is 17.5 liters.
The correct answer is 17.5 L17.5 \mathrm{~L}.

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