What number comes next in the series 5, 9, 13, 17, ... ?
Answer and explanation
Correct answer: D. 21
- Step 1: Find the differences: 9-5 = 4, 13-9 = 4, 17-13 = 4. Step 2. The gap is constant, so the next term is 17 + 4 = 21. Answer: 21. Why not the others: The gaps are always 4, so they neither grow, alternate nor double.
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