Classification (divisibility feature): Exactly one number is divisible by 11; the others are not. Identify the odd one out.

Introduction / Context:
Quick divisibility checks are common in classification problems. A routine trick is to test for divisibility by notable small primes such as 11. Among the options, one number is a clean multiple of 11, while the others are not. Spotting this property gives a fast and reliable route to the answer without heavy computation.

Given Data / Assumptions:

• 143 = 11 * 13.
• 217 = 7 * 31 (not divisible by 11).
• 241 = prime (not divisible by 11).
• 157 = prime (not divisible by 11).

Concept / Approach:
Use the 11-divisibility test or factor recognition. Only one number among the set is a multiple of 11, giving the required 3-to-1 split for an odd-one-out item.

Step-by-Step Solution:

Verification / Alternative check:
Perform the alternating-sum test for 11: for 143, (1 − 4 + 3) = 0 → divisible by 11.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming 217 = 11*19 (it is not); 11*19 = 209. Always verify.

Final Answer:
143