Proposed sums: 315423, 132354, and 252144
| Supposing that the sum chosen to be multiplied be that of | 132354 |
| And that the multiplicator be | 7 |
| ———— | |
| The product will then be | 926478 |
| ———— |
Suppose likewise that the figure which has been struck out is the 6, the remaining ones will form a sum of 92,478.
As you let the person who has done the multiplication set down the figures in the order he pleases, suppose also that he sets them down thus, on the piece of paper he gives you,
79,482.
When you pretend to smell the paper, add together in your mind the figures presented to you, in order to reduce them to nines; and say in your mind 7 and 2 make nine; after that 8 and 4 make 12; in 12 there is 9, and three remains towards 9 more; to complete which 6 is wanting, which is and must be the figure struck out. This calculation must be made quickly, and while you pass the paper under your nose under the pretext of smelling it.
There is another manner of proceeding to guess the figure left out, by letting the person chuse the sum he pleases to be multiplied, but then you must ask him to shew you the sum he means to have multiplied, and to let you add one figure at your option.
In that case, by running your eyes over the sum set down, you will easily see what figure you are obliged to add in order to complete the number of 9.