SOLUTION: You have 20 fl oz of a gas/oil mixture that is 2.5% oil. How much gas should you add to lower it to a 2% mix?

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Question 999143: You have 20 fl oz of a gas/oil mixture that is 2.5% oil. How much gas should you add to lower it
to a 2% mix?
Found 3 solutions by stanbon, josgarithmetic, Boreal:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
You have 20 fl oz of a gas/oil mixture that is 2.5% oil. How much gas should you add to lower it to a 2% mix?
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Equation:
oil + oil = oil
0.025*20 + 0*x = 0.02(20+x)
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Multiply thru by 1000 to get:
25*20 + 0 = 20*20+20x
20x = 5*20
x = 5 gallons (amt of pure gasoline to add)
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Cheers,
Stan H.
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Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
x, how much gas to add

20%2A2.5%2F%28x%2B20%29=2.0

Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
20*0.025=0.5 fl oz oil
That needs to be (0.02) of the total amount, x
0.02 is 1/50
So the same amount of oil, 0.5 fl oz, is 1/50 of the total amount of mix, so the total amount of mix is 25 ml.
You need to add 5 ml gas.
0.5/25=0.02 or 2%