Challenge: The Number Lock Heist — Level 5
The Number Lock Heist
Level 5 — The Solver | Ages 9–11 | Math | ⏱️ 10–12 minutes
This is a timed thinking challenge. You have limited attempts to crack the code. Every clue matters. No guessing — use logic.
📋 Challenge Rules
- You have 3 attempts to crack the lock
- Each wrong attempt costs 2 minutes from your timer
- Hints are available but add 1 minute to your final time
- No calculators — brain power only
- Explain your reasoning for each attempt
🔐 The Lock
Akuuu needs to open a 4-digit safe. Each digit is different. Here are the clues:
The first digit is half of the last digit. The last digit is even.
The second digit is 3 more than the first digit.
The third digit is the sum of the first and second digits. It is a single digit (less than 10).
All four digits add up to 20.
Think: Don’t guess random numbers. Start with what you KNOW for sure. Which clue gives you the tightest limits? Build from there.
🎯 Attempt 1
My code guess:
My reasoning (show your work):
The last digit must be even AND work with the “half” rule. What even numbers can be halved to make a single digit?
🎯 Attempt 2
What did I learn from Attempt 1?
My new code guess:
My revised reasoning:
If the first digit is X, the second is X+3, and the third is X+(X+3). The third digit must be less than 10. What is the maximum X can be?
🎯 Attempt 3 (Final)
Final code:
I am confident because:
⭐ Challenge Reflection
🧠 Thinking Pause
- I used clues to narrow possibilities instead of guessing
- I learned from my wrong attempt and adjusted my strategy
- I checked my final answer against ALL clues, not just one
🚀 Bonus: Design Your Own Lock
Create a 4-digit lock puzzle with 4 clues. It must have exactly ONE correct answer. Test it on a friend or family member.
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