Geo-Scientist Prelims GS strategy for every stream: what 720 PYQs say
Most of you on my Telegram channel are writing the Combined Geo-Scientist exam, and the question I get most is not about your own subject. It is about General Studies. Geologists, geophysicists, hydrogeologists and chemists all sit the same GS paper, and most of you are a little scared of it. So I took all 720 GS questions UPSC has asked from 2021 to 2026, put each one under a subject, and built the plan from what the papers actually ask. This post is the written version of the video, so you can come back to it while you study.
The whole strategy in three lines
- About 36% of the paper is Physics, Chemistry and Biology at school level. Any science graduate can collect these marks first.
- About 30% is Environment and Physical Geography. The same ideas come back year after year, so learn the repeated list.
- About 34% is Polity, History, Economy and current affairs. Read only a narrow list and attempt with elimination.
Why GS marks matter
The paper has 120 questions for 100 marks in 2 hours. A right answer gives 0.83 marks and a wrong one costs a third of that, 0.28. GS is not just qualifying: your score is counted in Stage I (out of 400), again in Stage II (Prelims 400 plus Mains 600) and in the final total out of 1200. For the Chemist stream, General category, the Stage I cut-off was 193 in 2024 and 167 in 2025.
My target for you is 50+. Attempt about 90 questions with 75 to 80% accuracy: 70 right and 20 wrong gives 52.8. If you push to 100 attempts and get only the same 70 right, you fall to 50. Ten extra wrong attempts cost you 2.8 marks, so accuracy matters more than the number of attempts.
The guessing rule
| Options you can cut | Expected marks | What to do |
|---|---|---|
| None (blind, 1 in 4) | 0.00 | Leave it |
| One (1 in 3) | +0.09 | Only if a second clue fits |
| Two (1 in 2) | +0.28 | Always attempt |
What the 720 PYQs say
| Subject | Questions, 2021–26 | Per paper |
|---|---|---|
| Geography | 111 | 18.5 |
| Physics | 109 | 18.2 |
| Environment | 109 | 18.2 |
| Chemistry | 85 | 14.2 |
| Current affairs | 75 | 12.5 |
| History | 70 | 11.7 |
| Polity | 64 | 10.7 |
| Biology | 64 | 10.7 |
| Economy | 33 | 5.5 |
Two things stand out. Physics doubled, from 10 questions in 2021 to about 20 a year since 2022, and many of them are Class 11–12 numericals. And science plus environment together make half the paper: 367 of the 720 questions.
Four tiers, four ways of preparing
- Tier A, collect: Physics, Chemistry, Biology, about 43 questions. Aim for 34 right.
- Tier B, the repeat zone: Environment and Geography, about 36 questions. Aim for 20 right.
- Tier C, narrow reading: History, Polity, Economy, about 28 questions. Aim for 12 right.
- Tier D, attempt smart: current affairs, 12 to 13 questions. Attempt only with elimination; 4 right is fine.
That is 70 right out of about 90 attempted: 70 × 0.83 − 20 × 0.28 ≈ 52.8. Tier A alone gives you about 28 marks, which is why science comes first in the plan. And use your stream: geologists get geomorphology, rocks and soils every year, geophysicists get about 18 physics questions, chemists about 14 chemistry questions.
One source per subject
- Chemistry: NCERT Science 9–10 chemistry chapters and the Class 11–12 basics. One day is enough.
- Physics: NCERT Physics 11–12, selected chapters, and every PYQ numerical.
- Biology: NCERT Science 9–10 and selected Class 11 Biology.
- Environment: NCERT Biology 12 ecology unit and selected chapters of Shankar IAS Environment.
- Geography: NCERT 11 Fundamentals of Physical Geography, India: Physical Environment, and a school atlas.
- Polity: selected chapters of M. Laxmikanth.
- History: NCERT Themes in Indian History I and II, and Spectrum for 1857 and 1905–1947.
- Economy: NCERT Economics Class 9 and Class 12 Macroeconomics (money and banking).
- Current affairs: any one monthly compilation from November 2025 to December 2026.
Do not add a second source until you have revised the first one twice. The PYQs are your real second source: all six GS papers are solved on this site, and you should solve them subject-wise, not year-wise.
The 11-week plan in short
Science first (weeks 1–2), then environment (weeks 3–4), physical and Indian geography with the atlas (weeks 5–6), polity (week 7), history (week 8), economy and current affairs (weeks 9–10), and only revision in the last days before the exam on 10 January 2027. Each week ends with the matching GS sectional test (G1 to G8), and the full GS mocks come near the end. Keep GS to about 1.5 to 2 hours a day.
In the exam hall
Work in three rounds. About 50 minutes for everything you know at once, about 40 minutes for the marked questions with elimination, and about 20 minutes to fill the OMR carefully. Keep 10 minutes in hand, and do not change an answer without a clear reason.
A word from me
Please do not try to master GS. Your Paper II subject is 300 marks and GS is 100, so give your subject about 75% of your time and GS the other 25%. In a heavy subject week, it is fine to cut GS to one hour a day. If you follow one source, the repeat list and the guessing rule, 50+ is well within reach for a science graduate of any stream. Write to me in the discussion group if you get stuck.
By VKC, your mentor. Integrated M.Sc. Chemistry, IIT Roorkee. CSIR NET Chemical Sciences, All India Rank 4. New posts are announced first on Telegram.