2025 · Q19
Let XYZ be a 3-digit number. Let D be the difference between XYZ and ZYX. What is the remainder when D is divided by 99?
Elementary MathematicsNumber System
- A0
- B1
- C7
- D9
Explanation
XYZ-ZYX=(100X+10Y+Z)-(100Z+10Y+X)=99(X-Z), always a multiple of 99. Remainder 0. The Y digits cancel - a common distraction.