The executor went to the neighbouring farm and asked to borrow a sheep for a few minutes. Then he returned to the sons and said, “Half of the (now) twenty sheep is 10. A quarter of the twenty sheep is 5. A fifth of the twenty sheep is 4. 10 + 5 + 4 = 19. Then the executor took the borrowed 20th sheep back to the neighbour.
I was visiting a friend one evening and remembered that he had three daughters. I asked him how old they were. “The product of their ages is 72,” he answered. Quizzically, I asked, “Is there anything else you can tell me?” “Yes,” he replied, “the sum of their ages is equal to the number of my house.” I stepped outside to see what the house number was. Upon returning inside, I said to my host, “I’m sorry, but I still can’t figure out their ages.” He responded apologetically, “I’m sorry, I forgot to mention that my oldest daughter likes strawberry shortcake.” With this information, I was able to determine all three of their ages. How old is each daughter?
The house number alone would have identified any of these groups. Since more information was required, we know the sum left the answer unknown. The presence of a single oldest child eliminates “2 6 6”, leaving “3 3 8” as the only possible answer.