Maths Olympiad Prep

Track / Stage 4 / 310 of 340 #570 of 1964

Problem 570

AMC 12 late, AIME early
Number theory Difficulty 5.0 Prove it

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.