Think of a number, multiply by six, divide by three, add forty, divide by two; name the result, and I will name the number thought of.
Method.—Multiplying by six and dividing by three gives twice the number; add forty we have twice the number, plus forty, divide by two we have once the number, plus twenty; hence, if I subtract twenty from the result he gives me I have the number thought of.
Let a person select a number greater than 1 and not exceeding 10. I will add to it a number not exceeding 10, alternately with himself; and, although he has the advantage in selecting the number to start with, I will reach the even hundred first.
Method.—I make my additions so that the sums are 12, 23, 34, 45, etc., to 89, when it is evident I can reach the hundred first. With one who does not know the method, I need not run through the entire series, but merely aim for 89, and when the secret of this is seen aim at 78, then 67, etc.
Think of a number of 3 or more figures, divide by nine, and name the remainder; erase one figure of the number, divide by 9, and tell me the remainder and I will tell you what figure you erased.
Method.—If the second remainder is less than the first, the figure erased is the difference between the remainders; but if the second remainder is greater than the first, the figure erased equals 9, minus the difference of the remainders.
Let a person think of any number on the dial face of a watch. I will then point to various numbers, and at each he will silently add one to the number selected, until he arrives at twenty, which he will announce aloud; and my pointer will then be on the number he selected.
Method.—I point promiscuously about the face of the watch until the eighth point, which should be on the “12.” I then pass regularly around toward the “1” pointing at “11,” “10,” “9,” etc., until “twenty” is called, when my pointer will be over the number selected.
Take nine from six and ten from nine and fifty from forty, and six will remain.
| SIX | IX | XL |
| IX | X | L |
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| S | I | X |