At first glance, this puzzle looks very simple—but thousands of people still give the wrong answer!
A man has 9 sons, and each son has a sister.
Now the question is:
How many people are there in the family?
Many people immediately calculate:
9 sons + 9 sisters + 1 father = 19 people
But that answer is wrong.
The key is hidden in the wording: “Each son has a sister.” It does not say that every son has a different sister. All nine sons can share the same sister.
So the family includes:
- 1 father
- 9 sons
- 1 daughter
Correct answer: 11 people
Some people may say the mother should also be included, making the answer 12, but the puzzle only mentions the man and his children. Therefore, based strictly on the given information, the best answer is 11.
This brain teaser tests careful reading rather than difficult mathematics. People often focus on the numbers and overlook the exact meaning of the sentence.
Did you get the correct answer on your first try? Comment your answer before checking the solution!