Find the next term in the pattern: 4, 7, 12, 19, 28, ? — use first differences to maintain the sequence’s internal arithmetic consistency.

Difficulty: Easy

Correct Answer: 39

Explanation:


Introduction / Context:
This classic “increasing differences” series often grows by consecutive odd numbers. Identifying that structure lets you extend the series cleanly.



Given Data / Assumptions:

  • Terms: 4, 7, 12, 19, 28, ?
  • We expect a steady progression in differences, likely simple odd increments.


Concept / Approach:
Compute first differences. If they form a recognizable arithmetic sequence, apply the next difference to obtain the next term.



Step-by-Step Solution:

Differences: 7 − 4 = 3; 12 − 7 = 5; 19 − 12 = 7; 28 − 19 = 9.The differences are 3, 5, 7, 9 — consecutive odd numbers.Next difference = 11.Next term = 28 + 11 = 39.


Verification / Alternative check:
All gaps are odd and increase by 2 each time; continuing with +11 yields a coherent continuation.



Why Other Options Are Wrong:

  • 30 or 36 would require smaller differences (2 or 8) that break the odd-number progression.
  • 49 would need a jump of +21, skipping the +11 step entirely.


Common Pitfalls:
Assuming multiplicative patterns too early. With short series, first differences provide the most reliable initial test.



Final Answer:
39


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