To make an addition before the Figures are set, by knowing only how many Figures are in each Row; as likewise how many Rows compose the whole; and then adding yourself some Figures equal to those that had been set.
Suppose the person had set five rows of figures, each row containing five figures.
Say in your mind, as you are making the addition beforehand, 9 times 5 make 45; set down 5 and carry 4: repeat the same thing for each of the five figures, as if they all counted 9; therefore for the second, say again, 9 times 5 make 45, and 4 carried over make 49; set down 9 and carry 4: in the same manner for the third, say 9 times 5 are 45, and 4 carried over are 49; set down 9 and carry 4: for the fourth do the same; and set down 9 and carry 4: for the fifth repeat the same, by setting down 9 and carrying 4.
Thus your addition being made before-hand will produce the sum of 499995: then shew this addition to every body in the company; and beg some one to do you the favour of laying on a paper 5 rows of numbers, containing five figures in each row.
EXAMPLE.
| Suppose the numbers set for you are the following: |
29971 14563 76382 37797 80130 |
| You ask leave to add a like quantity of numbers; in doing this, you take care that each of the figures you set down make 9 with each of the figures that have been given for you. |
70028 85436 23617 62202 19869 ———— 499995 ———— |
The first figure being 2, you must set 7; the second being 9, (which completes the number wanted) you must set a cypher (0); the third being the same, operate as before; the fourth being 7, set down 2; the fifth being 1, set down 8.
The second row beginning by 1, your first figure will be 8; the second number being 4, set down 5; the third being 5, put down 4; the fourth being 6, you must set down 3; the fifth being 3, set down 6.
As the third row begins by 7, begin yours by 2; under the 6 lay 3, then 1 under the 8, and 7 under the 2.