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GS Paper IUPSC Prelims 2001
Health & Medicine
Question No. 304Interactive Test Mode
00:00
+2-0.66

Q304. A radioactive substance has a half-life of four months. Three-fourth of the substance would decay in:

A radioactive substance has a half-life of four months. Three-fourth of the substance would decay in:

Select the correct option below (or cross out options to eliminate)
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Official Answer Key & Detailed Solution

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Official UPSC Answer KeyUPSC Prelims 2001 • Science and Technology

Correct Answer: Option (C) — 8 months

Concept & Option Breakdown

Standard Reference Verified

The decay of a radioactive material follows first-order kinetics:

  • After 1 half-life (4 months), 1/2 of the original substance remains (1/2 has decayed).
  • After 2 half-lives (4 × 2 = 8 months), (1/2)² = 1/4 remains, meaning 3/4 (75%) has decayed. Therefore, 3/4th of the substance decays in 8 months.
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Question Specifications & Syllabus Mapping

Examination & YearUPSC Civil Services Preliminary Examination 2001 (Q304)
Paper & Marking SchemeGS Paper I • 2 Marks (-0.66 Negative for incorrect response)
Syllabus Subject & TopicScience and Technology → Health & Medicine
Official Answer KeyOption (C) — 8 months

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Frequently Asked Questions — UPSC Prelims 2001 Q304

What is the official answer for UPSC Prelims 2001 GS Paper I Question 304 (Science and Technology)?

The official UPSC answer key for this 2001 Science and Technology (Health & Medicine) question is Option (C): "8 months". Correct attempts carry 2 Marks with -0.66 Negative penalty for wrong answers.

Which UPSC Prelims syllabus topic does this 2001 question belong to?

This question belongs to GS Paper I under the subject "Science and Technology" and micro-topic "Health & Medicine". You can explore all repeated questions from Health & Medicine in Acme AI's 3D Prelims PYQ Realm or practice 50 full-length and sectional tests in the APT Prelims Test Series.

How can I solve this Health & Medicine UPSC Prelims question using option elimination?

To solve Health & Medicine questions in UPSC Prelims, identify extreme modifiers, verify core NCERT conceptual definitions, and eliminate mutually contradictory statement pairs before locking your final option.

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