Lesson 07 · Maths · Constraint riddle
Step 1 of 4
Find the wrong step
Your lessonConstraint riddleStretch
The Dragon Vault Riddle
A dragon guards a two-digit vault code. The digits add to 11, and the tens digit is exactly 3 greater than the ones digit.
- Clue 1
- The digits total 11
- Clue 2
- Tens digit = ones digit + 3
Your question
What is the two-digit vault code?
Lumi’s answer: “The code is 47.”
1
Step 1 of 4
Find the wrong step
Find where the reasoning first breaks
Start with Step 1 and move downward. Choose the first line that stops making sense.
Later lines may be wrong too. Pick the first mistake.
Lumi’s work
These lines form one solution. Read them from top to bottom.
- 1
Let the ones digit be x, so the tens digit is x + 3.
- 2
Use the sum clue: x + (x + 3) = 11, so x = 4.
- 3
The ones digit is 4 and the tens digit is 7.
- 4
Write 4 first because it was solved first, making the code 47.