Number series (alternating *2 and +3): 5, 10, 13, 26, 29, 58, 61, (…) Find the next term by following the repeat pattern of operations.

Difficulty: Easy

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

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