From: null@void.com   
      
   You are folk of many and diverse talents.   
      
   In my outbuilding, to get up to the space above the horizontal roof   
   beams, I need a ladder exactly 3366mm length.   
      
   That's   
      
   (/ 3366 25.4 12) ;; 11.043307086614172 ;; ft   
   (- (/ 3366 25.4) (* 11 12)) ;; 0.5196850393700743 ;; inches   
      
   11ft length   
      
   In explanation   
      
   * 3120mm floor to roof-beam base vertically   
   * 1-to-4 rule - 1 length "out" for 4 lengths of height   
   * which means length of ladder is sqrt(17/16) of vertical height   
     (comes from "Pythagoras")   
      
   So   
      
   (+   
    (*   
     (sqrt (/ 17.0 16)) ;; 1.0307764064044151   
     3120) ;; 3216.0223879817754   
    100 ;; mm ;; the height of the roof beams   
    50 ;; just a bit more   
    ) ;; 3366.0223879817754   
      
   The idea is, that allows me to carry that ladder into the outbuilding   
   readily, then tip it upright and "catch" whichever roof-beam I want it   
   to lean against.   
      
   Then I can leave that ladder propped up vertically against the far   
   wall without being long enough to hit the roof.   
      
   How would one arrive at a ladder of exactly that length?   
   Any advice?   
      
   Rich S   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)