In the following question, each option shows a pair of numbers. In three of the pairs the second number is 25 more than the first number. Select the pair that does not follow this rule (odd number pair).

Introduction / Context:
This is a numerical reasoning question focused on identifying a consistent relationship between two numbers in each pair. Odd one out problems like this are common in aptitude tests because they quickly check whether the candidate can recognise a simple arithmetic pattern such as a constant difference between numbers. The goal is to find which pair breaks the shared rule and therefore stands out as different.

Given Data / Assumptions:
- The number pairs are 65 - 90, 73 - 97, 112 - 137, 162 - 187, and 45 - 70.
- Each option shows two numbers separated by a hyphen, which indicates a relationship between the first and second number.
- We assume basic arithmetic operations such as addition and subtraction are used to connect the numbers in each pair.
- Exactly one pair does not fit the common rule that the other pairs follow.

Concept / Approach:
The most direct approach is to check the difference between the second and first number in every pair. If three or four pairs show the same difference, that difference defines the main pattern. Any pair with a different difference value will then be the odd one out. This type of reasoning builds confidence with sequences and simple linear relations, which appear frequently in quantitative aptitude sections.

Step-by-Step Solution:
Step 1: For 65 - 90, compute 90 - 65. The result is 25.Step 2: For 112 - 137, compute 137 - 112. The result is also 25.Step 3: For 162 - 187, compute 187 - 162. The result again is 25.Step 4: For 45 - 70, compute 70 - 45. This difference is 25 as well.Step 5: Now consider 73 - 97. Compute 97 - 73. The result is 24, not 25.Step 6: Since four of the pairs show a difference of exactly 25 but the pair 73 - 97 shows a difference of only 24, 73 - 97 does not follow the rule and is the odd one out.

Verification / Alternative Check:
To verify quickly, we can also check by mental addition. Adding 25 to the first number in each pair should give the second number if the pair follows the rule. For 65, 65 + 25 = 90. For 112, 112 + 25 = 137. For 162, 162 + 25 = 187. For 45, 45 + 25 = 70. However, for 73, 73 + 25 = 98, which is not equal to 97. This alternative perspective confirms that 73 - 97 does not fit the pattern and so must be the correct answer as the odd one out.

Why Other Options Are Wrong:
65 - 90 is not odd because the second number is exactly 25 greater than the first number. 112 - 137 is also consistent with the pattern since the difference is 25. 162 - 187 follows the same rule with a difference of 25. 45 - 70 again shows a difference of 25 and fits the main pattern. None of these pairs break the rule, so they cannot be chosen as the odd one out.

Common Pitfalls:
Candidates sometimes miscalculate simple differences, especially under time pressure, and may think that 97 - 73 equals 25. Another mistake is to look for more complicated relationships such as ratios or squares when a simple constant difference is enough. In exam settings, always test for basic operations like addition and subtraction first, because they are often used to create these straightforward odd one out questions.

Final Answer:
73 - 97