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