Sunday

September 21, 2014

September 21, 2014

Posted by **Mia** on Thursday, February 14, 2013 at 2:27pm.

a. If 50% of the miles you drive are on the highway and 50% are around town, what is your overall average miles per gallon?

b. If 60% of the miles you drive are on the highway and 40% are around town, what is your overall average miles per gallon?

- Algebra 2 -
**JJ**, Thursday, February 14, 2013 at 4:37pma. Since the miles are equal, then you can just average your gas mileage.

b. This will be a weighted average.

Say you travel 100 miles.

60(30) + 40 (25) =

Divide that answer by 100.

- Algebra 2 -
**Steve**, Thursday, February 14, 2013 at 4:40pmif you drive c city miles and h highway miles, the gas you use is

c/25 + h/30 gallons

so, for a 50-50 mix

100mi/(50/25+50/30)gal = 27.27 mi/gal

and for a 40-60 mix

100mi/(40/25+60/30)gal = 27.77 mi/gal

extra credit:

So, what would the mix have to be to get 29 mi/gal?

- Algebra 2 -
**Steve**, Thursday, February 14, 2013 at 4:46pmJJ's solution sounds simple, but the reality is not. This is just like the usual work problems. If A can do a job in 2 days, and B can do it in 4 days, you can't just average 2 and 4 to get 3 days.

Instead, 1/both = 1/A + 1/B = 1/2 + 1/4 = 3/4

So, together they do the job in 4/3 days.

Makes sense, since A alone can do it in 2 days, any help from B will reduce the time it takes, not average out to 3 days.

Same for the gas mileage.

50 miles at 25gal/mi = 2 gal

50 miles at 30mi/gal = 1.6667 gal

so, 100 miles takes 3.6667 gal, or 27.27 mi/gal

- Algebra 2 -
**Mia**, Sunday, February 17, 2013 at 12:04pmThank you so much, Steve!!!! I really appreciate your help!!

**Answer this Question**

**Related Questions**

Math - Linear Equations - A car gets 21 mi/gal in city driving and 28 mi/gal ...

Math - Could someone answer this question so I understand it. The answer is 28.0...

calculus - An automobile computer gives a digital readout of fuel consumption in...

Math - 1. Solve the proportion: z z+9 ---- = ---- 3 12 A. 4 b. 3 c. 2 d. 1 my ...

Math - Omar owns a car and a moped. He can afford 12 gal of gasoline to be split...

word problem - Millwood city is constructing a new highway through town. The ...

algebra - given two containers, one holding 4 gal. and the other holding 3 gal. ...

math - Convert --→ 14 qt _____ gal. Choose the best answer from the ...

Math - I am having an issue with this problem: Subtract: 8 gal 7 qt - 3 gal 2 qt...

math - LPG (liquedfied petroleum gas) is stored in highly insulated spherical ...