170 



ON THE EARLY 



VI. To multiply numbers between 10 and ioo s when the digits in the 

 place of tens are different Multiply the tens of the smaller number 

 into the larger number ;. add to the result, the product of the units of the 

 smaller number into the tens of the greater ; call the sum tens ; add to 

 this the product of the units into the units. For example, to multiply 23 

 into 34, add 9 to 68, add 12 to 770.. 



VIL To multiply two unequal numbers, half the sum 'of which is 

 simple (Miifrid,) take the sum of the two and multiply half of it into 

 itself. From this product, subtract the square of half the difference of 

 the two numbers. For example, to multiply 24 by 36. From 900 sub- 

 tract the square of half the difference of the numbers, that is $6< There 

 remains 864*. 



For multiplying numbers consisting each of several places of figures* 

 the method described by this author, under the name of Shabacah or net 

 work, and illustrated by the following example, may have suggested the 

 idea of Napier's bones„ 



Multiply 62374 by 207.. 



'6 % 3 7 4 



g 



1 / 



/& 



/§ 



V4 1/8 







/ 



.a 



/\/ 





7 



4 / 



y% 



1/1 2/ 



4/ 



x! 



2 



9 1 



8 



