Problem #PRU-65266

Problemas Probabilidad y estadística Teoría de probabilidades Distribución discreta Métodos Principio extremal Ordenación en orden creciente (decreciente)
 13–16  3.0

Problem

On each of four cards there is written a natural number. Take two cards at random and add the numbers on them. With equal probability, this amount can be less than 9, equal to 9 or more 9. What numbers can be written on the cards?