Number series (alternating *2 and +3): 5, 10, 13, 26, 29, 58, 61, (…) Find the next term by following the repeat pattern of operations.
Aptitude
Odd Man Out and Series
Difficulty: Easy
Choose an option
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A122
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B64
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C125
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D128
Answer
Correct Answer: 122
Explanation
Introduction / Context:Alternating-operation series are common: the same two steps repeat—typically a multiplication followed by an addition. Recognizing this cycle quickly yields the next term.
Given Data / Assumptions:
- Series: 5, 10, 13, 26, 29, 58, 61, (…)
- Observe pairing of operations between successive terms.
Concept / Approach:Identify a repeating pattern: ×2 then +3. Validate across all transitions, then apply to compute the next term.
Step-by-Step Solution:
5 × 2 = 10.10 + 3 = 13.13 × 2 = 26.26 + 3 = 29.29 × 2 = 58.58 + 3 = 61.Next operation is ×2: 61 × 2 = 122.Verification / Alternative check:Continue one more hypothetical step: 122 + 3 = 125 would be the following term, confirming the cycle consistency.
Why Other Options Are Wrong:
- 64, 125, 128: These correspond to misapplied steps (+3 at the wrong time or different multipliers).
Common Pitfalls:Applying +3 twice in a row or reversing the order. Always mark the positions of operations to avoid a mismatch.
Final Answer:122