How to Write the Paper: The 3-Hour Plan

The 15 minutes of reading time

You cannot write from 10:15 to 10:30, but you can plan the whole paper.

By 10:30 every choice is made and you know where the long questions are.

The 3-hour plan

Physics gets a few more minutes than Chemistry for the same marks because of its numericals and ray diagrams. If you are behind at 12:15, do not rush Physics; take the time from checking. A numerical with every step shown is worth more than a quick look over MCQs.

The order to attempt questions

1. Divide the answer book first. Before you write any answer, head the first page "Section A: Biology". Start Section B and Section C each on a fresh page with its own heading. Never write an answer in another subject's section.
2. Answer in the paper's order: A, then B, then C. It keeps the sections separate without any effort. Starting with your strongest subject and leaving blank pages for the others is risky: if the space you left runs out, answers end up in the wrong section. Stick to A-B-C.
3. Inside a section, do the 1-mark questions first, spending about a minute on each. If one needs longer, mark it on the question paper, leave a line and come back.
4. Then the written questions, the ones you are sure of first, leaving space for the rest. Write each question number clearly in the margin.
5. Never leave a question blank. In the last 25 minutes, go back to anything skipped and write what you can: the formula, the diagram, the balanced equation. Each carries marks on its own.

The 1-mark questions

• There is no negative marking (the 2025 paper says so in its instructions), so answer every MCQ and Assertion-Reason question, even when you have to make your best guess.
• Statement-combination MCQs give three or four statements and ask which are correct, with options such as "(i) and (iii) only". Judge each statement true or false on its own first and mark it on the question paper. Then strike out every option that includes a false statement or leaves out a true one; usually only one option survives.
• Read every word of the question: "incorrect", "not", "least" and "respectively" decide the answer.

Small things that matter

• Write the Q.P. code printed on the question paper on the title page of your answer book. The front page of the paper asks for it.
• How much to write (a guide, not a rule): about 30-50 words for a 2-mark answer, 50-80 for 3 marks and 80-120 for 5 marks, plus any diagram or equation that is asked for. A longer answer does not earn more; the value points do.
• Hindi-medium students: the question paper is printed in both Hindi and English. If a Hindi term is unclear, read the same line in English.

Presentation that earns marks

• Chemical equations: always balanced. Add state symbols where they help, especially in displacement and precipitation reactions: $\mathrm{Fe(s) + CuSO_4(aq) \rightarrow FeSO_4(aq) + Cu(s)}$. Write conditions such as heat, conc. $\mathrm{H_2SO_4}$ or a catalyst over the arrow. A word equation is not a chemical equation.
• Numericals: write the given values with units, the formula, the substitution and the answer with its unit, each on its own line. Use the sign convention every time: distances are measured from the pole or optical centre, and distances in the direction of the incident light are positive, so a concave lens or concave mirror has a negative focal length.
• Units: Ω, V, A, W, kWh, J, cm, D (dioptre). A focal length without a unit, or a power worked out with the focal length in cm, loses marks.
• Ray diagrams: pencil and ruler, arrows on every ray, the principal axis, F and 2F (or F and C) marked, the image drawn and labelled.
• Biology diagrams: a clean outline, the labels asked for, straight label lines that don't cross, and a title. Flow charts (reflex arc, food chain) need arrows in the right direction.
• Point-wise answers: a 3-mark answer is usually three points. Number them. For "give reasons", write one clear reason per part, not a restatement of the question.
• Box or underline the final answer to every numerical.

Common ways students lose marks

1. Unbalanced equations. $\mathrm{H_2 + O_2 \rightarrow H_2O}$ earns less than $\mathrm{2H_2 + O_2 \rightarrow 2H_2O}$. Count every atom on both sides before you move on.
2. Signs in the lens formula. A concave lens of focal length 20 cm has $f = -20$ cm. Using +20 gives a wrong image distance, and every later step goes wrong with it.
3. Power of a lens with f in cm. $P = \frac{1}{f}$ needs $f$ in metres: a convex lens with $f = 50$ cm has $P = \frac{1}{0.5} = +2$ D, not 0.02 D.
4. Rays without arrows, or a ray bending the wrong way at a lens. Draw the two standard rays and check that the image matches the object's position.
5. Energy units. $1\ \mathrm{kWh} = 3.6 \times 10^6\ \mathrm{J}$. The cost of electricity uses kWh ("units"), not joules.
6. Series and parallel mixed up. In parallel the combined resistance is less than the smallest resistor. If your answer is bigger, recheck.
7. Mendel's ratios. A monohybrid F2 is 3 : 1 by appearance (phenotype) but 1 : 2 : 1 by genes (genotype). Say which one the question asks for.
8. The 10% law applied at the wrong step. If producers have 10,000 J, the third trophic level gets 100 J (10% twice), not 1,000 J.
9. Unlabelled or wrongly labelled diagrams. Label exactly the parts the question names; extra labels earn nothing.
10. Answers in the wrong section. A Physics answer written in the Chemistry part risks being missed.
11. Assertion-Reason on autopilot. Choosing (a) whenever both statements look familiar. Check whether R really explains A.
12. "Give reasons" answered with a fact. "Aluminium does not corrode easily" is not a reason. "A thin layer of aluminium oxide forms on its surface and protects it" is.

Case-based questions and OR choices

Case-based questions (Q15, Q28 and Q38, 4 marks each)

• The case is usually an experiment, a named student's observations, a real device or a short passage, sometimes with a table or graph.
• Parts (a) and (b) are 1 mark each and usually need one fact or one step. Answer in two or three lines.
• The last part is 2 marks with an internal choice. Its label differs from paper to paper: C or D in the sample paper, (c) OR (c) in February 2026, (c)(i) OR (c)(ii) in 2025 and May 2026. Answer only one; if both are answered, examiners usually mark only the first.
• The 2-mark part often asks "what will happen if the experiment is changed" or "is the inference still correct". Give the answer (yes or no, increase or decrease) and then the reason; the reason carries most of the marks.
• Read the numbers in the case carefully. Case-based questions often hide the data you need in a table or a graph.

ORs in the long answers and short questions

• Decide during the reading time. Choose the option where you know every part, including the diagram if one is asked for.
• In a 5-mark OR, the two options are complete questions. Do not mix parts from (A) and (B).
• If you change your mind halfway, cross out the abandoned attempt with a single line and write the new option's label clearly. A crossed-out attempt is not marked; if both are left, only the first is marked.