Pick the odd number: Three numbers are divisible by 9; one is not. Identify the number that is NOT divisible by 9.
Verbal Reasoning
Classification
Difficulty: Easy
Choose an option
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A72
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B45
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C81
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D28
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ENone of these
Answer
Correct Answer: 28
Explanation
Introduction / Context:Divisibility rules help quickly classify numbers. A number is divisible by 9 if the sum of its digits is divisible by 9. Three of the options satisfy this; one does not.
Given Data / Assumptions:
- Options: 72, 45, 81, 28.
- Rule: If digit sum is a multiple of 9, the number is divisible by 9.
Concept / Approach:Compute digit sums and check divisibility by 9 for each option.
Step-by-Step Solution:
72 → 7 + 2 = 9 → divisible by 9.45 → 4 + 5 = 9 → divisible by 9.81 → 8 + 1 = 9 → divisible by 9.28 → 2 + 8 = 10 → not divisible by 9.Verification / Alternative check:Perform direct division: 72/9 = 8, 45/9 = 5, 81/9 = 9, but 28/9 is not an integer.
Why Other Options Are Wrong:They are divisible by 9 and hence do not answer the prompt.
Common Pitfalls:Forgetting or misapplying the digit-sum rule, especially under time pressure.
Final Answer:28 is not divisible by 9 and is the odd number.