At the beginning of the year, the odometer on an SUV reads 37,266 miles.

Question

At the beginning of the year, the odometer on an SUV reads 37,266 miles. At the end of the year,  it reads 52,446 miles.  If the car averaged 23 miles per gallon, how many gallons of gasoline did it use during the year

Answer 1

Kim, Correct numbers, but you've forgotten to do your "unit chase".

 

We subtract the odometer numbers to find out how far we traveled during the year.

52446 miles - 37266 miles = 15180 miles

 

We want to cancel out the miles and solve for gallons.

So in our unit chase, whatever we do to our 15180 miles, we must put miles in the denominator to cancel them out... And we must put gallons in the numerator to keep that as our answer.

 

23 miles/gallon is the same as 1 gallon/23 miles

 

so...

15180 miles *   1 gallon

          year      23 miles

 

Rearranging a little, as we can by the commutative law of multiplication....

 

15180*1    *    miles   *   gallon

  23                miles         year

 

600           *       1      *     gallons

                                        year

 

600 gallons/year

 

Answer 2

1. Subtract the odometer readings. 52446-37266=15180

2.  Divide 15180 by 23

3. Answer 660