Choose the odd number: In 39, 83, 78, and 52, three numbers are multiples of 13; one number is not and is also prime. Identify this distinct number.
Verbal Reasoning
Classification
Difficulty: Easy
Choose an option
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A39
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B83
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C78
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D52
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ENone of these
Answer
Correct Answer: 83
Explanation
Introduction / Context:Spotting a specific divisor often solves a classification item quickly. Here we focus on 13.
Given Data / Assumptions:
- Numbers: 39, 83, 78, 52.
- Fact: 39 = 3 * 13, 78 = 6 * 13, 52 = 4 * 13.
Concept / Approach:Identify multiples of 13 and isolate the remainder.
Step-by-Step Solution:
39, 78, 52 → all divisible by 13.83 → not divisible by 13 and has no smaller prime divisors → prime.Verification / Alternative check:13 * 6 = 78, 13 * 4 = 52, 13 * 3 = 39. Nearest to 83 are 78 and 91; hence 83 is not 13k, and trial division up to sqrt(83) confirms primality.
Why Other Options Are Wrong:They are exact multiples of 13 and so share a property that 83 lacks.
Common Pitfalls:Assuming “larger” means composite; size alone is irrelevant.
Final Answer:83 is the odd number.