Question 423870
How much pure water must be mixed with 4 pints of 50% developer to produce a mixture that is 39% developer?
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How much pure water must be mixed with 4 pints of 50% developer to produce a mixture that is 39% developer?
4 pts of 50% contain 2 pts of developer and 2 pts of water.
If that 2 pts of developer is 39%,
2 pt = 0.39S  (S = total solution)
S = 2/0.39 =~ 5.128 pts
5.128 - 4 = 1.128 pts of water to add
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I'll do the other one later, or you can repost it.
Posting more than one problem at a time usually results in waiting longer for help, btw.