Question: There were two men standing on a street. The one says to the other, "I have 3 daughters, the product of their ages is 36. What is the age of the OLDEST daughter?"
The second guy says, "I need more information." So, the first guy says, "The sum of their ages is equal to the address of the house across the street."
The second guy looks at the address and says, "I still need more information." So, the first guy says, "My oldest daughter wears a red dress."
Answer:
First you need to find all the possible sets of three numbers that when multiplied equals 36:
1 1 36
1 2 18
1 3 12
1 4 9
1 6 6
2 2 9
2 3 6
3 3 4
Then you add the numbers together to find the sum
1 1 36 = 38
1 2 18 = 21
1 3 12 = 16
1 4 9 = 14
1 6 6 = 13
2 2 9 = 13
2 3 6 = 11
3 3 4 = 10
Even though we don't know the address the guy knows it. For him to need more information that means that at least two of the sets of numbers has the same sum. Two of them do, 1 6 6 and 2 2 9.
When the first guy said that his OLDEST daughter wears a red dress that meant that there had to be the oldest. So 1 6 6 can't possibly be the answer. So the possible possibility is 2 2 9 and the OLDEST daughter is 9 years old.
Therefore, the answer is 9.