A 25% alcohol solution is mixed with a 55% alcohol solution to create 12 liters of a 45% alcohol solution. What is the volume of the 25% solution used?
Answer Choices
Correct answer marked belowSee the full step-by-step explanation
You can see the correct answer above. Sign in for free to unlock the complete worked solution.
Track your performance and improve
Get detailed analytics, unlock full explanations, and move up difficulty tiers as you practice.
Official Explanation
Read the full explanation
Sign in for free to see the complete step-by-step solution to this question.
Thank for sharing!
Great!
Wait, why is it not 5? I keep getting confused between the amount of 25% and the amount of 55%. Can someone clarify which one the question is actually asking for?
It asks for the 25% volume specifically. Read the last line carefully, it says 'volume of the 25% solution used.' Easy to mix up.
same mistake lol. I solved for the other one first and it wasn't even an answer choice, that's how I caught it.
Is there a faster way than doing the whole weighted average calculation? Like can I just estimate since the target is closer to 55%?
Yeah, since 45 is closer to 55 than 25, the 55% solution should be the bigger portion, so the 25% one has to be smaller. That knocks out a couple choices fast.
What it tests
Your ability to reason about weighted averages and the composition of mixtures.
Common trap
Averaging the percentages of two solutions without weighting by their volumes.