If he selects the 4 request him to multiply by 36 and the result will be
Whichever figure he selects, mentally multiply it by 9 and request him to multiply the row by the result. If he thinks 9 the most imperfectly made figure, you, of course, tell him to multiply by 81 and the result will be all 9's.
How can four 9's be written so that they will make 100?
Ask some one to start a sum in addition by writing the top line of four figures. We will suppose he writes 1912. You mentally subtract the 2 and place it before the 1, making 21,910, which figures write on a piece of paper, which you fold up and lay on the table. You then ask a second person to place four figures under the first line. Then add a line yourself, which must be a deduction of the second line from four 9's. Ask a third person to add four figures to those already written. Then add another line yourself, making it a deduction of the third person's figures from four 9's. Request a fourth person to add up the sum and tell him you have already done so, and he will find the answer on the table. The sum will appear something like this:--
Which answer corresponds with the figures on the paper, which has been on the table the whole time. If you have in the company two friends upon whom you can rely as confederates, previously arrange with them to write the third and fifth lines, explaining to them that they must deduct the line immediately preceding theirs from 9's and make their lines the products. This adds greatly to the mystery of the trick.
Take 9 from 6; from 9 take 10, and from 40 take 50, and you will find 6 remains.
FROM SIX | FROM IX | FROM XL TAKE IX | TAKE X | TAKE L S | I | X
Thirteen commercial travellers arrived at an inn, and each desired a separate room. The landlady had but 12 vacant rooms, which may be represented thus:--
---------------------------------------------------- | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | ----------------------------------------------------
But she promised to accommodate all according to their wishes. So she showed two of the travellers into room No. 1, asking them to remain a few minutes together. Traveller No. 3 she showed into room No. 2, traveller No. 4 she showed into room No. 3, traveller No. 5 into room No. 4, traveller No. 6 into room No. 5, and so on until she had put the twelfth traveller into Room No. 11. She then went back to where she had left the two travellers together, and asking the thirteenth traveller to follow her, led him to No. 12, the remaining room. Thus all were accommodated. Ask your friends to explain the mystery.