Multiple choice

Find the missing term in the following number series. ? 53 108 185 284 405

  1. 16

  2. 18

  3. 20

  4. 15

  5. 24
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C Correct answer
Explanation

Working backwards from 53: differences are 55 (108-53), 77 (185-108), 99 (284-185), 121 (405-284). These are consecutive odd numbers. Before 53, subtract 7: 53 - 7 = 46. But 46 isn't an option. Testing forward from each option: 20 + 33 = 53, 53 + 55 = 108, 108 + 77 = 185, 185 + 99 = 284, 284 + 121 = 405. The pattern is odd numbers starting from 33: 33, 55, 77, 99, 121 (increasing by 22 each time).

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