Identify the odd number: Three options are divisible by 3, while one is not. Choose the number that is not a multiple of 3.

Introduction / Context:
Divisibility rules are quick tools for classification. A number is divisible by 3 if and only if the sum of its digits is divisible by 3. Here, three numbers satisfy this rule; one does not. Identify the non-multiple of 3.

Given Data / Assumptions:

• Candidates: 15, 63, 143, 195.
• Digit-sum test for divisibility by 3 applies.

Concept / Approach:
Compute the sum of digits for each number and test whether that sum is a multiple of 3. This avoids longer division and works reliably for base-10 integers.

Step-by-Step Solution:

Verification / Alternative check:
Direct division: 15/3 = 5, 63/3 = 21, 195/3 = 65 are integers, while 143/3 is not an integer. Hence 143 fails the test.

Why Other Options Are Wrong:
They are multiples of 3 and thus do not satisfy the condition of being the non-multiple.

Common Pitfalls:
Assuming that numbers ending in 5 are not divisible by 3; 195 is divisible by 3 because its digit sum is 15. Always use the digit-sum test.

Final Answer:
143 is not divisible by 3 and is the odd number.