Combined Codes

Multiple coding rules are applied in sequence.

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Multiple coding rules are applied in sequence.

Combined codes apply multiple transformations in sequence. For example, first reverse the alphabet, then shift by 2. Or first convert to numbers, then apply an operation. These are more complex because you must apply each rule in the correct order. The key will usually show the final result.

Apply Rule 1 to get intermediate result, then apply Rule 2 to get final result

Reverse then shift 1: A→Z→A (reverse gives Z, shift gives A)
Shift 2 then reverse: A→C→X (shift gives C, reverse gives X)
Number + 5: A=1+5=6, B=2+5=7, etc.

How to recognize it

Key doesn't match any single simple pattern
May need to work backwards to identify rules
Look for two-step transformations in examples

Common mistakes

Applying rules in the wrong order
Trying to find a single rule when two are needed
Not checking your work by encoding back

Step-by-step walkthrough

Encode 'AB' using: first shift +2, then reverse alphabet

Step 1: Apply shift +2 to A → C
Step 2: Reverse alphabet on C → X (C is 3rd, X is 3rd from end)
Step 1: Apply shift +2 to B → D
Step 2: Reverse alphabet on D → W (D is 4th, W is 4th from end)

Answer: XW

Practice guidance

Coding & Decoding