Guess my number. It is a 3-digit number near 120 whose mirror image is the same number. Where is the mirror kept?
Step 1: Numbers near 120 include 100-140.
Step 2: Use only digits 0, 1, 8 for same mirror image.
Step 3: For 3-digit number, first and third digits must be same.
Step 4: 111 is near 120 and has same mirror image.
Answer: The number is 111.
The mirror is kept in the middle (after the middle digit), so the first digit reflects as the third digit.
Explanation
The chapter presents this as a puzzle. Numbers near 120 that have the same mirror image must use digits 0, 1, or 8. The number 111 fits because when a mirror is placed in the center, the first digit (1) reflects as the third digit (1), and the middle digit (1) remains unchanged.
Solution Steps
Step 1: Numbers near 120 include 100-140
Step 2: Use only digits 0, 1, 8 for same mirror image
Step 3: For 3-digit number, first and third digits must be same
Step 4: 111 is near 120 and has same mirror image