Classification (numbers – perfect squares): Three numbers are perfect squares; one is not a perfect square. Identify the odd number.
Verbal Reasoning
Classification
Difficulty: Easy
Choose an option
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A47
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B64
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C225
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D4
Answer
Correct Answer: 47
Explanation
Introduction / Context:This item checks rapid recognition of perfect squares. Among the given numbers, three are squares of integers, while one is not. Your task is to pick the non-square at a glance using common square values.
Given Data / Assumptions:
- 4 = 2^2.
- 64 = 8^2.
- 225 = 15^2.
- 47 is not an integer square (sqrt(47)≈6.855...).
Concept / Approach:Recall squares up to at least 20^2 and match. Alternatively, factorize: a perfect square’s prime exponents are all even.
Step-by-Step Solution:
Confirm 4, 64, 225 are squares.Evaluate 47: prime and not a square.Therefore, 47 is the odd one out.Verification / Alternative check:Take square roots: only 4, 64, 225 yield integer roots; 47 does not.
Why Other Options Are Wrong:
They are perfect squares and thus do not meet the “non-square” criterion.Common Pitfalls:Confusing 225 with 250 or 256 (16^2). Remember 15^2=225.
Final Answer:47