Rated MPG for Confusion:
Using Gas Mileage to Learn Graphing and Data Analysis Skills
by
Claudia Bode, Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, KS
Alan Gleue, Science Department, Lawrence High School
Carolyn Pearson, Science Department, Bonner Springs High School
Part I – A Drop in the Bucket
Cody’s 16th birthday is this Friday. He’s psyched because he’s finally getting his unrestricted driver’s license. His parents have decided to let him drive to school instead of having to take the school bus.
Cody’s parents, Mr. and Mrs. Andrews, have two cars—a Toyota Corolla and a Jeep Grand Cherokee SUV. They use the Corolla for driving to work and running errands around town. It is a very economical car and gets 28 miles per gallon (mpg) around the city. However, Mr. and Mrs. Andrews need the larger SUV to haul around their two big St. Bernard dogs. The Jeep Grand Cherokee SUV gets 13 mpg around the city.
The problem is that the price of gas keeps going up. To save money, the Andrews have decided to trade one of their cars for a more fuel-efficient vehicle. They have come up with two options:
Keep the SUV and trade in the Corolla for a Toyota Prius Hybrid (the Prius makes 48 mpg in the city); or
Keep the Corolla and trade the SUV for a Minivan (they have their eyes on either a Toyota Sienna or Honda Odyssey; both of these models make 17 mpg city driving).
Put yourself in the place of Cody’s parents. You have two possible decisions. You could keep the SUV and trade in the Corolla for the Hybrid. Going from 28 (Corolla) to 48 (Hybrid) miles per gallon (mpg) should really save money on gasoline. That is a change of 20 mpg! Or, you could trade the SUV for the Minivan and keep the Corolla. The SUV gets about 13 mpg and the Minivan achieves slightly better gas mileage at 17 mpg. That is a change of only 4 mpg!
Questions
Without doing any calculations, what car do you think Cody’s parents should trade in? Should they keep the SUV and trade the Corolla for the Hybrid or should they keep the Corolla and trade the SUV for the Minivan? Offer a hypothesis on the trade that will save them the most money in gasoline. Offer an explanation for your hypothesis.
If you were Cody’s parents, what other factors might affect your decision about what type of car you would let Cody drive?
Date Posted: August 26, 2009.
Image credit: 1930s gas pump, licensed ©Jgroup | Dreamstime.com.
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