4. Can 19 different positive integers be found, the sum of whose digits is equal, and whose sum is 1999?
This one wants a proof. Work it on paper, then read the official solution and mark
yourself. Be honest about it: the record is only any use to you if it is.
Official solution
Hint: It cannot. Using property (1), we know these numbers are congruent to 1 modulo 9. Mimicking Example 3, we can enumerate to prove it.
Source: NuminaMath-1.5,
licensed Apache-2.0.
Statement and solution reproduced as published; topic, difficulty and ordering added
by this site.