Find the odd number pair from the following alternatives based on whether the second number is exactly twice the first.

Introduction / Context:
This odd one out question involves simple multiplication relationships inside number pairs. Three pairs follow a rule where the second number is exactly twice the first, while one pair does not, making it the odd pair.

Given Data / Assumptions:

• Pairs: 36 - 72, 17 - 34, 28 - 49, 24 - 48.
• We look for a pattern where second = 2 * first.
• All numbers are positive integers, so comparison is easy.

Concept / Approach:
The approach is straightforward. For each pair, divide the second number by the first or multiply the first by 2, and see whether the equality holds. If three pairs satisfy second = first * 2 and one does not, the one failing the rule is the odd pair.

Step-by-Step Solution:
36 - 72: 2 * 36 = 72, so the rule holds. 17 - 34: 2 * 17 = 34, so the rule also holds. 24 - 48: 2 * 24 = 48, again following the doubling rule. 28 - 49: 2 * 28 = 56, not 49, so this pair does not follow the doubling rule. Hence 28 - 49 is the only pair that does not satisfy second = 2 * first.

Verification / Alternative check:
Another way to verify is to compute the ratio second / first. For 36 - 72, 72 / 36 = 2; for 17 - 34, 34 / 17 = 2; for 24 - 48, 48 / 24 = 2. For 28 - 49, however, 49 / 28 is not an integer and certainly not equal to 2. This confirms that the third pair breaks the simple multiple rule followed by the others.

Why Other Options Are Wrong:

• 36 - 72: Follows the rule second = double of first, so it fits with 17 - 34 and 24 - 48.
• 17 - 34: Another clean example of the doubling relationship.
• 24 - 48: Also satisfies the same doubling rule without exception.

Common Pitfalls:
Some candidates may be distracted by the fact that 49 is a square number (7^2) and try to invent a more complex rule. In many aptitude questions, the intention is to reward quick recognition of simple patterns like doubling rather than complicated number theory. Focusing on the simplest consistent relation usually leads to the correct answer faster.

Final Answer:
28 - 49