Curifold Puzzle School · FREE PRACTICE SHEET
Work backwards from a clue
Reverse a sequence of operations and check the answer forwards.
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Your puzzle
A fictional number machine starts with a whole number from 1 to 10. It doubles the number, then adds 3. The display shows 17. Find the starting number by undoing the steps.
- The starting number is a whole number from 1 to 10.
- Double it, then add 3.
- The result is 17.
| Stage | Action | Value |
|---|---|---|
| Display | Known output | 17 |
| Undo addition | Subtract 3 | Your answer |
| Undo doubling | Divide by 2 | Your answer |
Record the original operations
Undo the last operation first
Write each intermediate value
Check the allowed input range
Run my answer forwards
andrew-stinson.com/learn/puzzle-school/work-backwards-from-a-clue/ · 2026-10-06