Mixing task: Determine ratio?

Question

Hi everyone, the important result is D. However, I'm not quite sure how to proceed. I wanted to add up the existing ml first, and that gives me 800 ml. And the mixed solution has a ratio of 1:9, so that means we have 10 parts in total, right?

But should I use the existing solutions below? Or how would you have done it?

best regards

picus48 · Answer

Yes, the solution d) is correct.

Solution 1 with 3/7 thus has 3 parts of alcohol to 10 parts=30%
Solution 2 with 1/9 has 10%
Solution 3 with 2/23 has 8%

5mL of 800mL = 5/800 * 30% = 1.875%
250mL of 800mL = 250/800 * 10% = 3.125%
Of solution 3, 500 mL of 800 mL=500/800 * 8%=5.0%

Makes 10%.