“Odd or Even”

Suppose that a person take an even number of coins or counters, or any such in one hand, and an odd number in the other, there is a simple method by which to tell in which hand the even number is. Ask the person to multiply the number in the right hand by an odd number, and the number in the left hand by an even number; then tell the person to add the two products together and tell you if the sum total be odd or even. If the sum be even, the even number is in the right hand, and if it be odd the even number is in the left hand.

Miscellaneous Notes and Queries, January 1892