Number series – find the next two terms: 8, 11, 21, 15, 18, 21, 22, ?, ?

Introduction / Context:
This sequence interleaves short growth spurts with resets, forming 3-term blocks. We must identify the block logic and extend it to obtain the next two numbers.

Given Data / Assumptions:

• Series: 8, 11, 21, 15, 18, 21, 22, ?, ?
• Visually, terms group as (8, 11, 21), (15, 18, 21), then a new block starting at 22.
• Within each 3-term block, the first two steps are small then moderate increases.

Concept / Approach:

Each block tends to start near the prior block’s end and then grows by a small step of +3 followed by a slightly larger step. In block 1: +3 then +10. In block 2: +3 then +3 (a smaller second step). The third block starts at 22; following the pattern, take +3 and then a modestly larger step (here +4) to continue the tempered growth trend.

Step-by-Step Solution:

Verification / Alternative check:

The emerging pattern uses a +3 starter step repeatedly (11→, 18→, 22→) followed by a moderate second step. Choosing 25 and 29 aligns with that recurrence.

Why Other Options Are Wrong:

25 18 and 25 21 reverse or flatten growth prematurely; 24 21 contradicts the +3 starter step from 22; 22 26 repeats the previous value and ignores the block starter rule.

Common Pitfalls:

Forcing a single constant difference fails; the series uses block-based increments with periodic resets and a recurring +3 lead step.

Final Answer:

25 29