What is the missing term in the following series: 11, 12, 17, 18, 23, 24,

Question

What is the missing term in the following series:

11, 12, 17, 18, 23, 24,

1. A. 27
2. B. 29 (Correct answer)
3. C. 30
4. D. 35

Correct Answer

Option B — 29

Detailed Solution & Explanation

The correct answer is 29.

Key Points

• Examine the differences: 11 → 12 is +1, 12 → 17 is +5, 17 → 18 is +1, 18 → 23 is +5, 23 → 24 is +1.
• The pattern alternates +1, +5, so the next step is +5: 24 + 5 = 29.

Additional Information

• Alternating-difference series are common; the giveaway is a difference row that itself repeats rather than progressing.
• Method: always write the row of differences first. If it repeats, the series alternates; if it progresses arithmetically, the series is second-order.
• A useful cross-check here: the terms pair off as (11, 12), (17, 18), (23, 24) — consecutive pairs rising by 6.