2 Replies Latest reply on Sep 25, 2012 5:10 PM by Joe Kuzich

# ratio relationship

Hello everyone,

One of my co workers is trying to set up a model & drawing that will automatically adjust the spacing of rafters in a hip roof.

The goal is to enter in a length (say 'X') and width (say 'Y') for the roof and get the spacing (say 'Q' because 'Z' is too predictable).

He has noticed that a relationship that stays consistent but can figure out how to mathematically write it out.  I feel like it's on the tip of my mind teasing me but I can't get it.

One of the relationships is X=180, Y=70 & Q=112.5  If we add or subtract to X the same happens to Q.  Add 2" to X and it adds 2" to Q.  If we add or subtract to Y the opposite happens to Q.  Add 2" to Y and it subtracts 2" from Q.  Does anyone know what formula I would need to write to express these relationships?  If so will you please share it with me?

Joe

• ###### Re: ratio relationship

try Q=X-Y+2.5"

it seems to fit the inputs you have given, though I have never layed out a roof before.

• ###### Re: ratio relationship

LMAO  I knew it was going to be simple, but I just could not break the fog in my head.  And to think its only Tuesday.  Thanks Jeremy that's perfect.