Question : Directions: In the following question a series is given, with one number missing. Choose the correct alternative from the given ones that will complete the series.
5, 11, 24, 51, 106, ?
Option 1: 122
Option 2: 217
Option 3: 120
Option 4: 153
Correct Answer: 217
Solution :
Given:
5, 11, 24, 51, 106, ?
Multiply each term by 2 and add consecutive natural numbers to get the next term of the series –
(5 × 2) + 1 = 10 + 1 = 11;
(11 × 2) + 2 = 22 + 2 = 24;
(24 × 2) + 3 = 48 + 3 = 51;
(51 × 2) + 4 = 102 + 4 = 106;
(106 × 2) + 5 = 212 + 5 = 217
So, the missing number of the series is 217. Hence, the second option is correct.
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