Moving from 10mpg to 20mpg is a 100% increase in efficiency, just like moving from 20mpg to 40mpg. For any given distance, however, moving from 10mpg to 20mpg will save twice as much gas as moving from 20mpg to 40mpg. To save as much gas as moving from 10mpg to 20mpg, a car would have to jump from 20mpg to infinity mpg. The question as presented is somewhat loaded, but what can you expect from a business school other than a bunch of misleading crap.
Slashdot Mirror
Determining the amount of gas saved per increase in mpg is not the same as computing the increase in efficiency.
10mpg = 10gal/100mi
20mpg = 5gal/100mi
40mpg = 2.5gal/100mi
Moving from 10mpg to 20mpg is a 100% increase in efficiency, just like moving from 20mpg to 40mpg. For any given distance, however, moving from 10mpg to 20mpg will save twice as much gas as moving from 20mpg to 40mpg. To save as much gas as moving from 10mpg to 20mpg, a car would have to jump from 20mpg to infinity mpg. The question as presented is somewhat loaded, but what can you expect from a business school other than a bunch of misleading crap.