SOLUTION: How do I dilute a 90% solution to 70%? Example: I have 8oz. of 90% solution. How much water do I add to make it a 70% solution?

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Question 376748: How do I dilute a 90% solution to 70%? Example: I have 8oz. of 90% solution. How much water do I add to make it a 70% solution?
Found 3 solutions by Fombitz, amalm06, ikleyn:
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let A be the amount of pure water (0% solution).
0%28A%29%2B90%288%29=70%28A%2B8%29
720=70A%2B560
70A=160
highlight%28A=16%2F7%29 ounces

Answer by amalm06(224) About Me  (Show Source):
You can put this solution on YOUR website!
The basic equation is:
(0.90)(8)+0=(0.70)(8+x)
Solving for x will give you the required amount of water

Alternatively, we can use the method of alligation
0.90-0.70=0.20
0.70-0=0.70
Then the ratio of solution to water=S/W=0.70/0.20
E.g. there are 0.70 parts of solution for every 0.20 parts of water
If there are 8 parts of solution, then 0.70/0.20=8/W
Solving for W, we have 2.2857oz of water (Answer)

Answer by ikleyn(52799) About Me  (Show Source):
You can put this solution on YOUR website!
.
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.
At the first turn read the lessons marked (*) in the list.

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.