# Thread: ratios, derivatives, and scale

1. i wonder why these things are called different things when they are basically the same written in 3 different ways.
look at this:

map scale: 1:1000 or 1cm on the map equals 1000cm in reality.
ratio : 1/1000 when the first number increase with 1, the second number increases with 1000.
derivative:
dx 1
= ____
dy 1000

if dx increases with 1, dy increases by 1000.

these basically do the same thing!
why do we have to learn the same thing 3 times?

wouldn't it be better to simply call it ratio instead of map scale and derivative as well?

2.

3. That is because they are not doing the same thing - for starters derivatives are local!!!

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