Question:medium

The strength of an indigo solution in percentage is equal to the amount of indigo in grams per 100 cc of water. Two 800 cc bottles are filled with indigo solutions of strengths 33% and 17%, respectively. A part of the solution from the first bottle is thrown away and replaced by an equal volume of the solution from the second bottle. If the strength of the indigo solution in the first bottle has now changed to 21% then the volume, in cc, of the solution left in the second bottle is

Updated On: Jan 15, 2026
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Correct Answer: 200

Solution and Explanation

Step 1: Solution Removal from First Bottle

Assume \( x \) cc of solution is removed from the first bottle. The quantity of indigo removed is:

\[ \text{Indigo Removed} = 0.33x \, \text{grams}. \]

The remaining solution volume in the first bottle is \( 800 - x \) cc, and the remaining indigo is:

\[ 0.33(800) - 0.33x = 264 - 0.33x \, \text{grams}. \]

Step 2: Solution Addition from Second Bottle

Subsequently, \( x \) cc of solution from the second bottle is added to the first. The indigo introduced from the second bottle is:

\[ 0.17x \, \text{grams}. \]

After this, the total volume in the first bottle remains 800 cc. The total indigo in the first bottle is now:

\[ 264 - 0.33x + 0.17x = 264 - 0.16x \, \text{grams}. \]

Step 3: Utilizing Solution Concentration

Following these actions, the solution concentration in the first bottle becomes 21%. Therefore, the indigo content in 800 cc of the solution is:

\[ 0.21 \times 800 = 168 \, \text{grams}. \]

The equation is formulated as follows:

\[ 264 - 0.16x = 168. \]

Step 4: Equation Solution

Solving the equation:

\[ -0.16x = 168 - 264 = -96, \]

\[ x = \frac{-96}{-0.16} = 600. \]

Step 5: Remaining Volume in Second Bottle

Thus, 600 cc of solution was taken from the second bottle.

The volume of solution remaining in the second bottle is calculated as:

\[ \text{Initial Volume} - \text{Volume Removed} = 800 \, \text{cc} - 600 \, \text{cc} = 200 \, \text{cc}. \]

Conclusion

Consequently, the volume of solution remaining in the second bottle is 200 cc.

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