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One way to begin thinking about this is to collect together some outputs and their corresponding inputs:
Can you write each step of the machine's instructions as a function machine?
What happens if you work backwards?
Your Number Was...
Age 11 to 14
Challenge Level 
One way to begin thinking about this is to collect together some outputs and their corresponding inputs:
| Finishing Number | Starting Number |
Can you write each step of the machine's instructions as a function machine?
What happens if you work backwards?
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