Length = the longer side
He wants to build a table with a length of 9ft.
The plans he has are 18ft x 36ft
Length of the plans = 36ft
Compare the length of the plans to the length he wants:
36 ft vs 9 ftThe length in the plans is 4 times longer than the length he wants.
Length he wants / Length of plans = your dilation scale factor
9 / 36 = ¼
1/4 = dilation scale factor
Hope this answers your question, and May the Force Be With You!
-Jabba