From Henry Dudeney’s Amusements in Mathematics, 1917. Without removing these checks from their ring, divide them into three groups so that the first group multiplied by the second makes the third. For example, one valid try might be 28, 907, 15463, except that 28 × 907 doesn’t equal 15463.

“Of course, you may have as many of the checks as you like in any group. The puzzle calls for some ingenuity, unless you have the luck to hit on the answer by chance.”