Number and figure tricks are generally a bit complicated for the people who are not good mathematicians, so this pert problem should afford some amusement if not mystification because it is easily followed.

A person is asked to jot down, one under the other, two figures of his own choice. Without drawing the usual line beneath the two numbers are added and the result put down. Then he adds together the last two figures and puts this result beneath. The last two figures are added and again the result put down. And this action is continued until there are ten numbers on the paper, one under the other.

The spectator is now told to draw a line beneath and add them all together for a final result. With either a single query or a glance, the performer is able to give the answer before the spectator can add the first column. It all depends upon the seventh number in the column, in the example, 71. This number, multiplied by 11 always gives the correct total for the column no matter what two numbers are used to begin. And 11 is a notoriously easy multiplier to be used in the mind. A subtle way of getting the information needed without asking directly for it is to turn away during the formation of the problem and wait for the spectator to signify that he’s through. You turn for but a split second and indicate that he is to draw a line and add them up. You have thus seen the seventh number and have ample time to make your calculation. You may finish as is your wont. He can pocket the total and receive the denouement later, or as you will.