Question by : can you properly explain a problem concerning ratios and such?
Is an article on why MPG should be changed to gallons per miles driven.
Not a bad idea, although everyone who totes it around as gallons per mile completely ruins any perceived benefit (my car gets .034 gallons per mile!)
anyway, my problem. The article points out how the majority of people believe that going from 34 MPG to 50 MPG saves more fuel than 18 MPG to 28 MPG, when this is in fact not the case.
driving 10 or 100 miles will show you that you save twice as many gallons switching from 18 to 28.
Numerically I get it and can see it, but not conceptually. So if in some more abstract way, can you explain WHY?
I am positive it has something to do with the fact that 34 and 50 are larger numbers therefore the larger difference (16>10) is of less importance. But that doesn’t explain it all really. What am I missing?
10 mpg over 10,000 miles- 1000 gal.
50 mpg over 10,000 miles- 200 gal
so its not that the fuel effieciecy is different, numerically its all even ofcourse. But why with the lower numbers, is the savings larger? it has something to do with ratios right>>>???
Answer by Andy
I suspect that you are missing the significance that the savings is in gallons, not miles. So consider gallons rather than miles per gallon.
Driver A drives, say, 12000 miles per year and gets 18 miles a gallon. 12000/18 = 666.66 gallons.
He buys a car that gets 28 miles per gallon, driving the same mileage. 12000/28 = 428.57 gallons
Gallons saved = 238.09
Driver B drives 12000 miles per year and gets 34 miles per gallon. 12000/34 = 352.94 gallons.
She buys a car that get 50 miles per gallon, driving the same mileage. 12000/50 = 240 gallons.
Gallons saved = 112.94
The function y = x is linear, but the function y = 1/x is non-linear. Gallons/mile is linear in gallons, but miles/gallon is non-linear in gallons.
Powered by Yahoo! Answers