UPSC Prelims 2026 · CSAT Paper 2 · Set DMathematicsQ 25 / 80

UPSC Prelims 2026 CSAT Paper 2 — Question 25

Question

How many three-digit numbers can be expressed as an integral power of 2?

(a)1
(b)2
(c)3
(d)4

UnlockIAS answer: (c)3

Solution

2⁷ = 128, 2⁸ = 256 and 2⁹ = 512 are the only powers of 2 between 100 and 999 (2⁶ = 64 is two-digit, 2¹⁰ = 1024 is four-digit). So there are 3.

UnlockIAS expert key, prepared 24 May 2026 and cross-verified by re-deriving the answer — this is our key, not the official UPSC provisional key (awaited).

Section

Mathematics

Topic Reference

Numeracy — Powers of 2

Official UPSC key still awaited

UPSC has announced (PIB Release 2262441, 18 May 2026) that the provisional answer key for CSE Prelims 2026 will be released “soon after Exam”. Until then, use the CSAT score calculator for your qualifying-status estimate, and join the per-question discussion below.

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Official Notification

PIB Release 2262441

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