Question 18
Châu writes a four-digit number and asks Dũng to guess it.
Dũng: “Is it 2896?”
Châu: “Exactly one digit is correct, and it is in the correct position.”
Dũng: “Is it 5273?”
Châu: “Exactly two digits are correct, but both are in the wrong positions.”
Dũng: “Is it 1702?”
Châu: “All four digits are correct, but all four are in the wrong positions.”
What number did Châu write?
Dũng: “Is it 2896?”
Châu: “Exactly one digit is correct, and it is in the correct position.”
Dũng: “Is it 5273?”
Châu: “Exactly two digits are correct, but both are in the wrong positions.”
Dũng: “Is it 1702?”
Châu: “All four digits are correct, but all four are in the wrong positions.”
What number did Châu write?