same. You can get out of the
difficulty, on being told you are wrong, by saying (in case you have
given 9), "Yes, I see it is a nought; I thought it had a tail, so
mistook it for a nine." If you have named 0 and it turns out to be 9,
you can say, "Oh, I didn't notice the tail; of course I should have said
nine."

A LESSON IN THE CORRECT FORMATION OF A FIGURE

Request a friend to write the following figures:--

1 2 3 4 5 6 7 9

Take the paper from him and, after pretending to scrutinise the row, ask
him to point out which figure he considers most imperfectly made. If he
should select the 1, say, "You had better practise making that figure.
Oblige me by multiplying the row by nine." When he does so the result
will be

1 1 1 1 1 1 1 1 1

Then say, "After this practice you will be able to make better ones in
future."

If he selects the 4 request him to multiply by 36 and the result will be

4 4 4 4 4 4 4 4 4

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.

FOUR NINES PROBLEM

How can four 9's be written so that they will make 100?

SOLUTION.

99 9/9

AN ANSWER TO A SUM GIVEN IN ADVANCE

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:--

1912
7234
2765
4891
5108
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