Civil Service Exam Reviewer · Number Series · hard

What number(s) should complete the series: 5, 25, 23, 529, ?

1. 279841
2. 531
3. 527
4. 525

Answer

C. 527

Solution

Alternately square and subtract 2: 5² = 25, −2 → 23, ² → 529, −2 → 527.

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