In the following number classification question, four three digit numbers are given. In three of the numbers, the sum of the digits is the same, while in one number the digit sum is different. Select the odd number from the given alternatives.

Introduction / Context:
This question belongs to the number reasoning and odd one out category. You are given four three digit numbers: 373, 265, 490 and 672. In many aptitude questions, numbers are grouped using properties such as sum of digits, divisibility or even odd status. Here, three numbers share the same digit sum, while one does not. Your task is to identify the number whose digit sum is different and mark it as the odd one out.

Given Data / Assumptions:

• Numbers: 373, 265, 490 and 672.
• We consider the sum of digits of each number.
• Exactly one number has a digit sum different from the others.
• No advanced mathematics is needed; only basic addition of digits is required.

Concept / Approach:
A well known technique in such problems is to compute the sum of the digits of each number and compare the results. Sometimes three numbers share an equal sum and one stands out, or three numbers share a property like divisibility while one does not. When you notice that sums are small and close to each other, this is usually a strong hint that the question revolves around digit sums rather than more complicated relationships.

Step-by-Step Solution:
Step 1: Compute the digit sum of 373.3 + 7 + 3 = 13.Step 2: Compute the digit sum of 265.2 + 6 + 5 = 13.Step 3: Compute the digit sum of 490.4 + 9 + 0 = 13.Step 4: Compute the digit sum of 672.6 + 7 + 2 = 15.Step 5: Compare the sums.373, 265 and 490 all have a digit sum of 13, while 672 has a digit sum of 15. Therefore, 672 does not match the pattern.

Verification / Alternative check:
As an alternative, you can notice that 373, 265 and 490 all reduce to the same digital root if you apply repeated digit sum reduction. For example, 373 gives 3 + 7 + 3 = 13 and 1 + 3 = 4, 265 gives 13 and again 4, and 490 gives 13 and then 4. However, 672 gives 15 and 1 + 5 = 6. Since the three numbers reduce to 4 while 672 reduces to 6, 672 clearly stands apart from the group under the same digit based operation, confirming it as the odd one.

Why Other Options Are Wrong:
373: Has digit sum 13, matching 265 and 490, so it belongs to the main pattern.
265: Also has digit sum 13 and is therefore not the odd number.
490: Once again has digit sum 13 and fits with the first two numbers.

Common Pitfalls:
Candidates sometimes begin checking properties like divisibility by 3, 5 or 9 or look for squares and cubes, which can waste time when the intended pattern is much simpler. Another small error is misadding digits, especially if you are working quickly under exam pressure. To avoid this, always double check your digit sums before drawing a conclusion, particularly when all sums are in the same range.

Final Answer:
The odd number is 672, because its digit sum is 15, whereas the digit sum of each of the other three numbers is 13.