SOLUTION: On his way home from the school board meeting, Kevin fills up his car. He likes the idea of using gasoline with ethanol but thinks his car can only handle 25% ethanol. At the gas s

Question 1183227: On his way home from the school board meeting, Kevin fills up his car. He likes the idea of using gasoline with ethanol but thinks his car can only handle 25% 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 Kevin use if he wants to fill up his car with 10 gallons of fuel containing 25% ethanol?

Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39625) (Show Source): You can put this solution on YOUR website!
v gallons of the 85% ethanol
10-v gallons of the 10% ethanol

-

.
.
Answer by greenestamps(13203) (Show Source): You can put this solution on YOUR website!

Here is an alternative method for solving 2-part mixture problems like this, if a formal algebraic solution is not required.

You are mixing 10% ethanol and 85% ethanol, and you want to get 25% ethanol.
Look at the three percentages on a number line and observe/calculate that 25% is 1/5 of the way from 10% to 85%. (10 to 85 is a difference of 75; 10 to 25 is a difference of 15; 15/75 = 1/5.)
That means 1/5 of the mixture needs to be the higher percentage ingredient.

ANSWER: 1/5 of 10 gallons, or 2 gallons, of the 85% ethanol; the other 8 gallons of 10% ethanol.

CHECK:
.85(2)+.10(8) = 1.7+.8 = 2.5
.25(10) = 2.5

RELATED QUESTIONS
On his way home from the school board meeting, Keith fills up his car. He likes the idea... (answered by Alan3354,ikleyn)
When Larry drove to his meeting his average speed was 50 mph. On the way home the weather (answered by jvan)
jai left home at 1:00pm on his way to a meeting 300 miles away. If he averages 60 miles... (answered by josmiceli)
Ryan is on his way home in his car. He has driven miles so far, which is four-fifths of... (answered by Alan3354)
Dale is on his way home in his car. He has driven 30 miles so far, which is... (answered by oscargut)
Charlie is on his way home in his car. He has driven 30 miles so far, which is two-thirds (answered by jim_thompson5910)
Ali is on his way home in his car. He has driven 12 miles so far, which is... (answered by macston)
Ivan is on his way home in his car. He has driven 20 miles so far which is four-fifths of (answered by fractalier)
After walking 1/4 mile from home, Han is 1/3 of his way to school. What is the... (answered by josgarithmetic,greenestamps)