Question : Directions: Select the number from among the given options that can replace the question mark (?) in the following series.
6, 11, 21, 41, 81, ?
Option 1: 241
Option 2: 151
Option 3: 161
Option 4: 240
Correct Answer: 161
Solution :
Given:
6, 11, 21, 41, 81, ?
The pattern is as follows –
(6 × 2) – 1 = 12 – 1 = 11
(11 × 2) – 1 = 22 – 1 = 21
(21 × 2) – 1 = 42 – 1 = 41
(41 × 2) – 1 = 82 – 1 = 81
(81 × 2) – 1 = 162 – 1 = 161
So, the missing number is 161. Hence, the third option is correct.
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