ANOTHER WAY.
Tell the person to take 1 from the number thought of, and then double the remainder; desire him to take 1 from this double, and to add to it the number thought of; in the last place, ask him the number arising from this addition, and, if you add 3 to it, the third of the sum will be the number thought of. The application of this rule is so easy that it is needless to illustrate it by an example.