AS PRACTISED BY THE ARABS. 119 



6. By Art. z.) since 80 = 10 a 3 so 80 -f- 80 = 160 = 10 a s -f. 10 a 3 

 — 20 a 3 , and is the sum written in the Rank of the Cube. 



/. By the transference of 160, its units are put under the 4th place of 

 the second period, and hence 20 a} thus transferred, is the upper number 

 in the Rank of the Cube. 



■a. Then by Art. 8.) since 8 — 4 « so 2 -j- 8 - 10 = «-f-4a = 5«, 

 and is the upper number in the Rank of the Latus. 



\. Then 10 X 2 — 20 — 5 a X a ■=. 5 a", and is the product written 

 in the Rank of the Square. 



p. By Art. £.) since 40 — 10 a 2 so 20 -f 40 = 60 — 5 a* -f 10 a 2 = 15 or, 

 and is the sum written in the Rank of the Square. 



v. By the transference of 60, its units are put under the 3d place of 

 the second period, and hence 15 a" thus transferred, is the upper number 

 in the Rank of the Square. 



|. Then by Art. X.) since 10 = 5 a so 2 -J- 10 = 12 ~ a -f 5 a — 6«, 

 and is the sum written in the Rank of the Latus. 



v. By the transference of 12, its units are put under the second place 

 of the second period, and hence 6 a thus transferred, is the upper number 

 in the Rank of the Latus. 



1. Then if there be a Digit annexed to the right hand of the upper 

 number in the Rank of the Latus, since by Art. if) this upper number 



h 1 



