Here's a good one. You don't need to be a mathematician to solve this one.
A man (and mathematician) wishes to know for each house in a street the number of children and their ages. At one house, he is greeted by a woman who tells him that she has three children whose ages multiply to give her age, 36. She also tells him that their ages add to the house number. The man makes a mental note of the house number, thanks the woman, and leaves. But on his way to the next house he realises that he still cannot work out the ages of the children. And so he returns to the house. The woman tells him, "The youngest one is at Grandma's house." The man smiles and notes down the ages of the children.
How old are the children? Explain your reasoning.
They are 2, 3 and 6. That's because I can't think of 3 other fairly close ages that multiply to give 36, unless the youngest was only 1. e.g: 1, 4 and 9 or 1, 2 and 18. However, I don't think one child could be 1, because then the age isn't actually being "multiplied " when combined with another age.
If the youngest was a twin like me (I'm 9 hours younger than my brother), then there would be two kids of 2 and one of 9, or two kids of 1 and one of 36, but I have a feeling they are to be three different ages. Also a 36 year old kid would be too old to have a grandmother in all probablility.
Unless it's the Grandmother of Horace, that is. Maybe Horace has two siblings....? No, the Grandmother there would be constantly out on the raz in her insatiable quest for lumberjacks and bourbon.