# Suppose a fuel mixture is 5% ethanol and 95% gasoline. How much ethanol (in gallons) must you add to one gallon of the fuel so that the new fuel mixture is 10% ethanol?

$\frac{5}{90} \left(.056 \left(3 \mathrm{dp}\right)\right)$ gallon of ethanol is added to make the mixture 10% ethanol.
In one gallon fuel mixture gasoline is $0.95$ gallon
In one gallon fuel mixture ethanol is $0.05$ gallon
let x gallon of ethanol is added to make the mixture 10% ethanol
$\therefore \left(x + .05\right) = \frac{10}{100} \left(1 + x\right) \mathmr{and} 100 x + 5 = 10 + 10 x \mathmr{and} 90 x = 5 \mathmr{and} x = \frac{5}{90}$ gallon of ethanol.[Ans]