Question 351742
Hi,
*Note: .10*30oz tells us how much benzalkonium chloride is in that total solution
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.10*30oz = 3oz  (there are 3 oz of benzalkonium chloride in that total solution)

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Question speaks of making a new 4% solution
Let x be the amount of that "total" solution
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.04*x = 3oz  (the actual amount of benzalkonium chloride stays the same)
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x = 3oz/.04 = 75oz
As we already have 30z of "total" solution, 45oz of water will need to be added
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check your answer
.04*75oz = the 3 oz of benzalkonium chloride in the "new total" solution