Choose the odd number: Among 43, 53, 63, and 73, three are prime and one is composite. Identify the composite number.
Verbal Reasoning
Classification
Difficulty: Easy
Choose an option
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A43
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B53
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C63
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D73
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ENone of these
Answer
Correct Answer: 63
Explanation
Introduction / Context:Most numbers in this set are primes; the single composite is the odd one out.
Given Data / Assumptions:
- Set: 43, 53, 63, 73.
- Primes around 40–80 are commonly tested.
Concept / Approach:Use digit-sum rule for 3 and quick small-prime checks.
Step-by-Step Solution:
63 → 6 + 3 = 9 → divisible by 3 → composite.43 → not divisible by 2, 3, 5 → prime.53 → not divisible by 2, 3, 5 → prime.73 → not divisible by 2, 3, 5 → prime.Verification / Alternative check:Direct division by 7: 63 = 7 * 9 confirms compositeness.
Why Other Options Are Wrong:They lack non-trivial divisors and are prime.
Common Pitfalls:Assuming “ends with 3” implies divisibility by 3; the rule concerns digit sums, not the last digit.
Final Answer:63 is composite and thus the odd number.