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Question : Directions: Select the number from among the given options that can replace the question mark (?) in the following series.
19, 39, 77, 155,  ?

Option 1: 288

Option 2: 236

Option 3: 309

Option 4: 311


Team Careers360 17th Jan, 2024
Answer (1)
Team Careers360 24th Jan, 2024

Correct Answer: 309


Solution : Given:
19, 39, 77, 155,  ?

Multiply the number by 2 and then add and subtract 1 alternately –
(19 × 2) + 1 = 38 + 1 = 39
(39 × 2) – 1 = 78 – 1 = 77
(77 × 2) + 1 = 154 + 1 = 155
(155 × 2) – 1 = 310 – 1 = 309

Thus, the required missing number in the series is 309. Hence, the third option is correct.

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