In the number sequence 123, 112, 133, 112, 143, which number is the odd man out if, in the correct pattern, the sum of the first two digits should equal the third digit?

Introduction / Context:
This question involves three digit numbers arranged in a small sequence: 123, 112, 133, 112, 143. You are asked to pick the odd man out. The key idea is to look at the relationship between the individual digits of each number rather than treating the numbers as ordinary values in an arithmetic series.

Given Data / Assumptions:
The numbers are:

• 123
• 112
• 133
• 112
• 143

We assume that a consistent rule links the first two digits to the third digit in four of these numbers, while one number breaks this internal digit sum rule.

Concept / Approach:
A natural pattern to test is whether the third digit equals the sum of the first two digits. For example, in 123, we can ask whether 1 + 2 equals 3. If this rule holds for most of the numbers in the list and fails for exactly one number, that exception will be the odd one out.

Step-by-Step Solution:
Step 1: Examine 123. The first two digits are 1 and 2. Their sum is 1 + 2 = 3, which matches the third digit.Step 2: Examine 112. The first two digits are 1 and 1. Their sum is 1 + 1 = 2, which matches the third digit.Step 3: Examine 133. The first two digits are 1 and 3. Their sum is 1 + 3 = 4, which matches the third digit.Step 4: Examine the repeated 112 again. As before, 1 + 1 = 2, which matches the third digit.Step 5: Examine 143. The first two digits are 1 and 4. Their sum is 1 + 4 = 5, but the third digit is 3, not 5. So 143 does not satisfy the sum rule.

Verification / Alternative check:
We can now see that four numbers, namely 123, 112, 133 and the second 112, follow the pattern: third digit equals the sum of the first two digits. The fifth number, 143, fails this test because the sum of its first two digits is 5, while the last digit is 3. There is no second consistent rule that would include 143 with the others, so it clearly stands out as different.

Why Other Options Are Wrong:
Numbers like 112 and 133 are completely consistent with the sum pattern. Removing any of them as the odd one would leave a set where 143 remains the only number not obeying the digit sum rule. Hence they cannot be considered the correct odd one out.

Common Pitfalls:
Some learners may look for patterns based on the overall numeric values or differences between numbers instead of examining digit relationships. In many reasoning questions involving multi digit numbers, the real pattern lies inside the digits rather than in the full number values. Always check for digit sums, products or positions when you see such sequences.

Final Answer:
The number that breaks the sum of first two digits equals third digit pattern is 143.