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 November 22nd, 2016, 10:26 AM #1 Newbie   Joined: Nov 2016 From: United States Posts: 1 Thanks: 0 help solve problem I have 30ml solution of 0.05%. How much water needed to add to make a solution of 0.04%? Once I have solution of 0.04%, how much water needed to add to make a solution of 0.03%? Thank you. Last edited by skipjack; November 22nd, 2016 at 12:08 PM.
 November 22nd, 2016, 10:59 AM #2 Math Team   Joined: Jul 2011 From: Texas Posts: 2,751 Thanks: 1401 x = mL of pure water 30(.05) + x(0) = (30+x)(.04) solve for x, then substitute the calculated value for x in the following equation ... y = mL of pure water (30+x)(.04) + y(0) = (30+x+y)(.03) solve for y
 November 22nd, 2016, 12:22 PM #3 Global Moderator   Joined: Dec 2006 Posts: 18,967 Thanks: 1607 Is the original solution 0.05% or 5%?
November 22nd, 2016, 12:29 PM   #4
Math Team

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Quote:
 Originally Posted by skipjack Is the original solution 0.05% or 5%?
doesn't matter as long as the other given concentrations are relatively the same ... true?

 November 22nd, 2016, 03:52 PM #5 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 12,448 Thanks: 832 It's this simple (w = water): .....30 @ 5 ......w @ 0 ======= 30+w @ 4 (30*5 + w*0) / (30 + w) = 4

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