For the Sam Yuan Xuan Kong Da Gua stream (64 Hexagrams method), the "sum-of-ten" method 合十數 法 as well as the "birth-result number match" method 生成數法 are applied for matching of the mountain dragon, sitting, facing and water in/out location gua (hexagram)'s Lo Shu 5 element qi (洛書五行氣)among each other.  
 
Lo Shu numbers into 5 elements: 1, 6 = water;  2, 7 = fire;  3, 8 = wood;  4, 9 = metal
 
1,2,3,4,5   = birth numbers
6,7,8,9,10 = result numbers
 
 
An example below with diagram is used for illustration of the use of "sum-of-ten" method:
 
si-hai facing,
- mountain dragon comes in from the gua at 181.5-184.5 degree 姤卦( 9),
- sitting gua is 154.5-157.5 小畜卦（2 ),
- facing gua at degree 331.5-334.5 豫卦（8）,
- water gua at degree 1.5-4.5 復卦（1）
 
As such, the sitting gua (2) with facing gua (8) come to the sum-of-ten, and the dragon (9) with water gua (1) come to the sum-of-ten too.  These four qua would be then of the same yun gua under the flying star 8 八運輔星, the terminology for this matching set is   via a direct translation into English would be "one gua pure clean".  
 
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而, 三元玄空大卦 （易六十四卦 ）也以龍山向水合十為吉。例如已山亥向, 來龍入首為姤卦（9）, 山為小畜卦（2）， 向為豫卦（8）， 水口為復卦（1）。 如此, 山向合十（2+8）， 龍水合十（9+1）。龍山向水名也屬左輔八星之內。
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