MathDB
odd sum of a 3-digit number with it's ''inverted'' 201& May Olympiad L1 p1

Source:

August 25, 2021
number theoryDigitsodd

Problem Statement

To each three-digit number, Matías added the number obtained by inverting its digits. For example, he added 729729 to the number 927927. Calculate in how many cases the result of the sum of Matías is a number with all its digits odd.