Question : Directions: Which number will replace the question mark (?) to complete the given series?
3, 7, 15, 31, 63, 127, ?
Option 1: 245
Option 2: 250
Option 3: 260
Option 4: 255
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Correct Answer: 255
Solution :
Given:
3, 7, 15, 31, 63, 127, ?
Add 1 to twice the previous number to get the next number of the given series –
(3 × 2) + 1 = 6 + 1 = 7;
(7 × 2) + 1 = 14 + 1 = 15;
(15 × 2) + 1 = 30 + 1 = 31;
(31 × 2) + 1 = 62 + 1 = 63;
(63 × 2) + 1 = 126 + 1 = 127;
(127 × 2) + 1 = 254 + 1 = 255
So, the missing number is 255. Hence, the fourth option is correct.
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