5 lbs book CH 16 Problem 18

[johnhurford]

Question on CH 16 problem 18: Can you please explain why you use regular gasoline as the 'original' amount? Or how one would know to use it as opposed to premium gasoline as the 'original' amount in the percent increase formula?

[tommywallach]

Hey John,

First off, Premium is the original here, not regular.

Beyond that, you have to follow the narrative of the question. In this case, they ask "Regular is what percent greater than premium."

If I ask "4 is what percent greater than 5?", then 5 is my original, because I'm using it as a benchmark. Think of it like someone is holding up 4 and asking it to be compared to 5. 5 is the original, and we want to see how 4 compares.

Hope that makes sense!

-t