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10 liters of the 15% alcohol drink contain 0.15*10 liters of pure alcohol.
If you add W liters of water, the mixture will contain the same 0.15*10 liters of alcohol, but the total liquid volume will be (10+W) liters.
You need to find W under the condition
= 0.05,
which is the condition that the mixture is 5% alcohol.
OK. You just have an equation.
To solve it, multiply both sides by (10+W). You will get
0.15*10 = 0.05*(10+W),
1.5 = 0.5 + 0.05W ====> 0.05W = 1.5 - 0.5 = 1 ====> W = = 20.
Answer. 20 liters of water must be added.
Check. = = 0.05 = 5%.
Solved.
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There is entire bunch of introductory lessons covering various types of mixture problems
- Mixture problems
- More Mixture problems
- Solving typical word problems on mixtures for solutions
- Word problems on mixtures for antifreeze solutions
- Word problems on mixtures for alloys
- Typical word problems on mixtures from the archive
in this site.
Read them and become an expert in solution mixture word problems.
Also, you have this free of charge online textbook in ALGEBRA-I in this site
- ALGEBRA-I - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this textbook in the section "Word problems" under the topic "Mixture problems".
Save the link to this online textbook together with its description
Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson
to your archive and use it when it is needed.