Problem #PRU-32046

Problemas Métodos Métodos algebraicos Contando de dos maneras Particiones en pares y grupos; biyecciones Principio del casillero Principio del casillero (otros)
 11–13  3.0

Problem

You are given 25 numbers. The sum of any 4 of these numbers is positive. Prove that the sum of all 25 numbers is also positive.