3 boxes: blue, white, red, and 9 numberd balls
Source: VII May Olympiad (Olimpiada de Mayo) 2001 L1 P3
September 22, 2022
combinatorics
Problem Statement
There are three boxes, one blue, one white and one red, and balls. Each of the balls has a number from to written on it, without repetitions. The balls are distributed in the boxes, so that there are at least two balls in each box. Then, in each box, add up all the numbers written on the balls it contains. The three outcomes are called the blue sum, the white sum, and the red sum, depending on the color of the corresponding box. Find all possible distributions of the balls such that the red sum equals twice the blue sum, and the red sum minus the white sum equals the white sum minus the blue sum.