Recursive construction – multiply by n and add n: 1, 2, 6, 21, 88, 445, ? — Find the next term.
Aptitude
Odd Man Out and Series
Difficulty: Easy
Choose an option
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A2230
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B2676
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C2580
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D2670
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E2680
Answer
Correct Answer: 2676
Explanation
Introduction / Context:Here each step multiplies by an increasing integer and then adds that same integer: ×1 +1, ×2 +2, ×3 +3, etc.
Observation / Approach:
- 1 × 1 + 1 = 2
- 2 × 2 + 2 = 6
- 6 × 3 + 3 = 21
- 21 × 4 + 4 = 88
- 88 × 5 + 5 = 445
- Next uses 6: 445 × 6 + 6 = 2676
Step-by-Step Solution:Compute 445 × 6 + 6 = 2670 + 6 = 2676.
Verification / Alternative check:The pattern of “×n then +n” is consistent from the first transition onward.
Why Other Options Are Wrong:Other values do not equal 445 × 6 + 6 and thus break the recursive rule.
Common Pitfalls:Using “×n + (n−1)” or a constant adder; both fail earlier steps.
Final Answer:2676