Sarah wants to buy the car that has a better mileage rating. Cars of Company A travel 20 miles per gallon and cars of Company B travel 14 km per liter.

[1 mile = 1.6 km; 1 gallon = 3.79 liters]

Part A: Which company's car should Sarah buy? Justify your answer by comparing the mileages after converting to the same units. 

Part B: If 10 gallons of gas is filled in the car which gives better mileage, and you went on a drive and checked on the gas used every 30 miles, describe appropriate scales on the x-axis and y-axis to graph the rate at which the car uses gas. 

Expert Answers

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Conversion is quite easy to do.  If you state the values as fractions and then cross-cancel the units conversion is a snap. 

To Convert Company A's cars from mpg to Km per Liter:

`(20mi)/(1 gal) xx (1.6 km)/(1 mi)=(32 km)/(1 gal) xx (1 gal)/(3.79 L)~~8.44` km per Liter. 

To convert Company B's cars for Km per liter, to Mpg:

`(14 km)/(1 L) xx (3.79 L)/1 gal=(53.06 km)/(1 gal) xx (1 mi)/(1.6 km)=33.1625` mpg

Either way, Company B's cars have better gas mileage. 


I would use the X-axis to show how many miles you've traveled, and I would scale it to increments of 10 miles.  The Y axis would show how much gas you have left, and scaled to increments of 1 gal.  Your graph should look like this. 

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