6

Part of 2017 Latvia Baltic Way TST

Problems(1)

naturals in 13x13 grid, sum of numbers at 8 squares divisible by 8

Source: 2017 Latvia BW TST P6

A natural number is written in each box of the

13 \times 13

grid area. Prove that you can choose

2

4

columns such that the sum of the numbers written at their

8

intersections is divisible by

8

combinatoricsdivisiblenumber theory