Free practice · single-choice · medium
Practice
Recognize an alternating pattern
Which number comes next: 3, 6, 5, 10, 9, 18, ...?
Alternating-rule test
Two operations repeat in a stable cycle
Proposed ruleAlternate ×2, then −1
- 3→×2→6Fits
- 6→−1→5Fits
- 5→×2→10Fits
- 10→−1→9Fits
ConclusionAfter 9 × 2 = 18, the next operation is −1, giving 17.
Alternating patterns must preserve both the operation and its position in the cycle.