Choose the odd number: In 11, 17, 45, and 37, three are prime numbers and one is composite. Identify the composite number.
Verbal Reasoning
Classification
Difficulty: Easy
Choose an option
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A11
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B17
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C45
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D37
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ENone of these
Answer
Correct Answer: 45
Explanation
Introduction / Context:This classification asks you to separate a composite number from a set of primes. Spotting quick divisibility helps.
Given Data / Assumptions:
- Candidates: 11, 17, 45, 37.
- Prime = two divisors; composite = more than two.
Concept / Approach:Check divisible-by-2, divisible-by-3 (digit-sum), and divisible-by-5 (ends with 0 or 5). Then confirm any remaining suspects with small primes.
Step-by-Step Solution:
11 → prime.17 → prime.45 → ends with 5 and 4 + 5 = 9; 45 = 5 * 9 → composite.37 → prime.Verification / Alternative check:Further factorization: 45 = 3 * 3 * 5 confirms composite status.
Why Other Options Are Wrong:11, 17, and 37 have no non-trivial divisors.
Common Pitfalls:Overlooking the easy 5-divisibility rule for numbers ending in 5.
Final Answer:45 is composite and is the odd number.