| The remanent | 3 | 0 | 9[8] |
| Wherof me shal with-draw | 3 | 1 | 2 |
| The nombre to be with-draw | . | . | 3 |
If the second figure is a cipher. And yf the vnyte wherof me shal borow be a cifre, go ferther to the figure signyficatife, and ther borow one, and retournyng bake, in the place of euery cifre þat ye passide ouer, sette figures of .9. as here it is specifiede:—
| The remenaunt | 2 | 9 | 9 | 9 | 9 |
| Wherof me shalle with-draw | 3 | 0 | 0 | 0 | 3 |
| The nombre to be with-draw | 4 |
And whan me comethe to the nombre wherof me intendithe, there remaynethe alle-wayes .10. ffor þe whiche .10. &c. A justification of the rule given. The reson why þat for euery cifre left behynde me setteth figures ther of .9. this it is:—If fro the .3. place me borowede an vnyte, that vnyte by respect of the figure that he came fro representith an .C., In the place of that cifre [passed over] is left .9., [which is worth ninety], and yit it remaynethe as .10., And the same resone wolde be yf me hade borowede an vnyte fro the .4., .5., .6., place, or ony other so vpwarde. This done, withdraw the seconde of the lower ordre fro the figure above his hede of þe omyst ordre, and wirche as before. Why it is better to work from right to left. And note wele that in addicion or in subtraccioun me may wele fro the lift side begynne and ryn to the right side, But it wol be more profitabler to be do, as it is taught. How to prove subtraction, And yf thow wilt prove yf thow have do wele or no, The figures that thow hast withdraw, adde them [ayene] to the omyst figures, and they wolle accorde with the first that thow haddest yf thow have labored wele; and addition. and in like wise in addicioun, whan thow hast addede alle thy figures, withdraw them that thow first Fol. 50 b. *addest, and the same wolle retourne. The subtraccioun is none other but a prouffe of the addicioun, and the contrarye in like wise.
Chapter IV. Mediation.
Definition of mediation. M[ediacioun] is the fyndyng of the halfyng of euery nombre, that it may be seyne what and how moche is euery halfe. In halfyng ay oo order of figures and oo nombre is necessary, that is to sey the nombre to be halfede. Therfor yf thow wilt half any nombre, write that nombre by his differences, and Where to begin. begynne at the right, that is to sey, fro the first figure to the right side, so that it be signyficatife other represent vnyte or eny other digitalle nombre. If it be vnyte write in his place a cifre for the If the first figure is unity. figures folowyng, [lest they signify less], and write that vnyte without in the table, other resolue it in .60. [mynvtes] and sette a-side half of tho minutes so, and reserve the remenaunt without in the table, as thus .30.; other sette without thus .dī: that kepethe none ordre of place, Nathelesse it hathe signyficacioun. And yf the other figure signyfie any other digital nombre fro vnyte forthe, oþer the nombre is ode or evene.
| Halfede | 2 | 2 |
| to be halfede | 4 | 4 |
| halfede | 2 | 3 | [di] |
| To be halfede | 4 | 7 |
What to do if it is not unity. If it be even, write this half in this wise:—
And if it be odde, Take the next even vndre hym conteynede, and put his half in the place of that odde, and of þe vnyte that remaynethe to be halfede do thus:—