Accumulation
Elements are progressively added without removing previous ones. Count increases monotonically.
Understanding this pattern
In accumulation patterns, each frame adds one or more new elements while keeping all existing ones. A grid might fill one cell per step, or pie slices expand by a fixed angle each frame. The prediction requires knowing where the next element appears — which often follows a secondary path or counting rule.
Example Question
Pattern Rule
In each successive frame, exactly one additional cell becomes shaded, and the shading accumulates by following a fixed path through the grid (e.g., left-to-right, row by row, or in a snake/spiral order). The total number of filled cells increases by one per frame, tracing that path sequentially.
Explanation
Option D is correct because it continues the strict +1 cell accumulation along the established traversal path: each frame fills the next cell in sequence, so the number of shaded cells equals the frame index and the positions form a contiguous trail. Option A is tempting because it has the right count but places the newest cell in the wrong grid position, breaking the path. Option B introduces a gap in the shading, implying a cell was skipped, which violates the sequential rule. Option C overshoots by adding two cells instead of one. Option E mirrors or reflects the pattern rather than extending it, a common distractor in path-accumulation questions where candidates mistake a spatial transformation for a sequential fill.
How to spot it
- The number of elements grows from frame to frame
- Nothing disappears between frames — only additions
- A region fills progressively (grid cells, pie slices, dots)
Common traps
- Assuming linear growth when the pattern adds 1, then 2, then 3
- Missing the path rule that determines WHERE new elements appear
- Confusing accumulation with replacement (elements change, not add)
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