Multiple choice

Find the missing term ‘?’ of the following series. 6, 9, 18, 45, 126, ?

  1. 313

  2. 369

  3. 350

  4. 320

  5. 309
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B Correct answer
Explanation

Pattern: multiply by consecutive odd numbers and add consecutive numbers. 6 × 1 + 3 = 9; 9 × 3 - 9 = 18; 18 × 5 + 15 = 105; 105 × 7 - 21 = 714; 714 × 9 + 27 = 6453... This doesn't match. Alternative: differences are 3, 9, 27, 81, 243 (powers of 3). 6 + 3 = 9; 9 + 9 = 18; 18 + 27 = 45; 45 + 81 = 126; 126 + 243 = 369.

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