Odd One Out — Among 24, 49, 80, and 15, choose the unique perfect square and justify why the others are not squares.
Verbal Reasoning
Classification
Difficulty: Easy
Choose an option
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A24
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B49
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C80
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D15
Answer
Correct Answer: 49
Explanation
Introduction / Context:Perfect-square recognition is a classic skill in number classification tasks.
Given Data / Assumptions:
- Numbers: 24, 49, 80, 15.
- Perfect square definition: equals n^2 for an integer n.
Concept / Approach:Check whether each candidate equals some small n^2.
Step-by-Step Solution:49 = 7^2, a perfect square.24 is between 4^2 = 16 and 5^2 = 25, not a square.80 is between 8^2 = 64 and 9^2 = 81, not a square.15 is between 3^2 = 9 and 4^2 = 16, not a square.
Verification / Alternative check:Prime-factor check: 49 = 7^2 has all exponents even; others do not.
Why Other Options Are Wrong:
- 24: not an integer square.
- 80: not an integer square.
- 15: not an integer square.
Common Pitfalls:Confusing proximity to a square (like 80 near 81) with being a square.
Final Answer:49