Classification – Pairs of numbers (perfect squares): three pairs are both perfect squares; one pair contains non-square numbers. Identify the odd one out. Options: 8 - 15, 25 - 36, 49 - 64, 81 - 100.

Introduction / Context:
Square-number recognition is a common classification basis. When pairs are given, the test may require both members to be perfect squares.

Given Data / Assumptions:

• 25 and 36 are 5^2 and 6^2.
• 49 and 64 are 7^2 and 8^2.
• 81 and 100 are 9^2 and 10^2.
• 8 and 15 are not perfect squares.

Concept / Approach:
Check square status of each number in every pair. The pair that fails the “both squares” rule is the outlier.

Step-by-Step Solution:
Verify 25–36 → both squares.Verify 49–64 → both squares.Verify 81–100 → both squares.Check 8–15 → neither is a square.

Verification / Alternative check:
Locate each value between consecutive squares: 8 is between 2^2 and 3^2; 15 is between 3^2 and 4^2.

Why Other Options Are Wrong:
25–36, 49–64, 81–100: Each pair consists entirely of perfect squares.

Common Pitfalls:
Confusing 16 (a square) with 15; careful reading avoids this slip.

Final Answer:
8 - 15