Art Benjamin recently gave a talk in which he performed the following trick: An audience member secretly picks a positive integer N whose digits are distinct and increasing. The audience member uses a calculator to compute 9N. The magician is able to divine the sum of the digits of 9N without knowing N. That's because that sum is always 9. Art tells me he learned this fact from an article in Mathematics Magazine (Vol 87, No 3, June 2014) called "Surprises, Surprises, Surprises", written by Felix Lazebnik. Lazebnik's statement is slightly more general: "Consider any positive integer N whose (decimal) digits read from left to right are in non-decreasing order, but the last two digits (tens and ones) are in increasing order. Prove that the sum of digits of 9N is always exactly 9." Lazebnik says that he heard about the problem from applied mathematician named Valery Kanevsky, who tells me he does not know the problem's provenance. Do any of you know anything about this? Jim Propp