Identify the odd number: In most three-digit numbers listed, the third digit equals the sum of the first two digits (ab + c rule). Choose the number that does NOT follow this property.

Introduction / Context:
This classification item uses a digit-based rule. For most options, the ones digit equals the sum of the hundreds and tens digits. One number fails this pattern; identify it.

Given Data / Assumptions:

• Numbers: 527, 639, 246, 356.
• Interpretation: For XYZ, check whether Z = X + Y.

Concept / Approach:
Break each number into digits and test the sum relation.

Step-by-Step Solution:

Verification / Alternative check:
Compute (last digit) − (sum of first two digits). Only 356 gives 6 − 8 = −2, confirming the mismatch.

Why Other Options Are Wrong:
They satisfy the defined digit-sum condition exactly.

Common Pitfalls:
Misreading digits or adding incorrectly (e.g., 3 + 5 mistaken as 6). Carefully parse each digit before adding.

Final Answer:
356 is the odd number.