Question : Directions: Which number will replace the question mark (?) in the following series?
12, 25, 51, 103, ?, 415, 831
Option 1: 208
Option 2: 207
Option 3: 206
Option 4: 200
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Correct Answer: 207
Solution :
Given:
12, 25, 51, 103, ?, 415, 831
Multiply the previous term by 2 and add 1 to the resultant term to get the next term.
(12 × 2) + 1 = 25; (25 × 2) + 1 = 51; (51 × 2) + 1 = 103; (103 × 2) + 1 = 207; (207 × 2) + 1 = 415; (415 × 2) + 1 = 831
So, 207 is the missing term in the series. Hence, the second option is correct.
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