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GATE 2024 Chemical Engineering, Q4 · General Aptitude

The correct answer is D, 31.

Question

Which one of the given options is a possible value of x in the following sequence? 3, 7, 15, x, 63, 127, 255

  • A. 35
  • B. 40
  • C. 45
  • D. 31

Official answer: 31

Why

GATE 2024 official key: (D). Each term is 2n−1:3=22−1,7=23−1,15=24−1,x=25−1=31,63=26−1,127=27−1,255=28−1.2ⁿ−1: 3=2²−1, 7=2³−1, 15=2⁴−1, x=2⁵−1=31, 63=2⁶−1, 127=2⁷−1, 255=2⁸−1.

Explanation cross-checked for consistency. Final answer matches the official IIT answer key.

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