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soniadiana2011
- Junior | Next Rank: 30 Posts
- Posts: 14
- Joined: Wed May 16, 2012 8:52 am
You are adding ethanol and the question is asking for its amount so track the amount of ethanol:
ethanol before: 5% of 20 gallons = (0.05)(20) = 1 gallon
ethanol added: x gallons (unknown for now)
ethanol in final mix: 10% of (20+x) gallons = 0.10(20+x) gallons
The balance equation:
ethanol before + ethanol added = ethanol in final mixture
1 + x = 0.10(20+x)
Simplify to 0.9 x = 1
Solve to x = 1/0.9 = 10/9 gallons of ethanol added.
