Question

On his way home from school board meeting , Keith fills up his car. He like the idea of using gasoline with ethanol , but think his car only handle 40% ethanol. At the gas station , he can use regular gas with 10% ethanol or E85 fuel with 85% ethanol. How many gallons of each type of fuel should Keith use if he wants to fill up his car with 10 gallons of fuel containing 40% ethanol ?

Answer 1

6 gallons regular gas with 10% ethanol and 4 gallons E85 fuel with 85% ethanol

Explanation:

In this case, we must test with values for each fuel class to arrive at the correct answer.

For example, 6 gallons of 10% ethanol and 4 gallons of 85% ethanol:

`\begin{gathered} 10\text{\% of 6 =}(10)/(100)\cdot6=0.6\text{ gallons of ethanol in it} \\ 85\text{\% of 4 =}(85)/(100)\cdot4=3.4\text{ gallons of ethanol in it} \\ \text{ Total ethanol in 10 gallons is 0.6 + 3.4 = 4 gallons }\rightarrow\text{ 4 gallons is 40\% of 10} \\ \text{Therefore, we have 10 gallons of fuel containing 40\% ethanol } \end{gathered}`