Assertion-Reason Questions in Class 10 Science: How to Solve

Two statements can both be true without one explaining the other. That is the distinction that makes an assertion-reason question different from an ordinary fact-check. If you recognise both statements from the same chapter and immediately choose "correct explanation", you can miss the relationship the question is testing.

This guide explains how to solve assertion-reason questions in Class 10 Science, using original electricity examples. CBSE's 2026-27 Science curriculum includes assertion-reasoning among its question types. Use the current syllabus and paper instructions rather than assuming that an older practice sheet has the same topics or answer code.

Read the answer options before solving

The official 2026-27 Class 10 Science sample paper uses these options for its assertion-reason questions:

• A: Both assertion and reason are true, and the reason correctly explains the assertion.
• B: Both are true, but the reason does not correctly explain the assertion.
• C: The assertion is true, but the reason is false.
• D: The assertion is false, but the reason is true.

These letters belong to that paper's instructions. Do not memorise a letter without its meaning. A worksheet from another source may arrange the choices differently. Check the wording beside the question you are actually answering.

Judge each statement before judging the link

Read the assertion on its own. Ask what scientific idea makes it true or false. Notice conditions such as constant temperature, the same material or a fixed potential difference. A sentence may sound familiar while leaving out a condition that matters.

Then read the reason independently. Do not accept it just because the assertion is true. Check a formula, a definition or a process from your textbook. If needed, write a short calculation in your rough work. Keep the two truth decisions separate until you have evidence for each.

When both are true, ask the remaining question: does this reason explain this assertion under the stated conditions? Being about the same chapter is not enough. Try joining the sentences with "because", then explain the scientific connection in your own words. A sentence that sounds smooth is not proof.

Original example: a reason that explains

The examples below are written for practice. They are not copied CBSE questions or predictions of the board paper.

Assertion: At a fixed potential difference, doubling the resistance halves the current.

Reason: For the circuit conditions described by Ohm's law, current equals potential difference divided by resistance.

The assertion is true under the stated conditions. If the potential difference is 6 V and resistance is 3 ohms, current is 2 A. With resistance increased to 6 ohms at the same 6 V, current becomes 1 A. The reason is also true: I = V/R gives that result directly. It explains the assertion, so the matching choice in the official sample paper's code is A.

Change the reason and test the relationship again

Keep the same assertion, but replace the reason with: "The equivalent resistance of resistors connected in series is the sum of their individual resistances."

That reason is true, but it does not establish why current halves when resistance doubles at fixed voltage. The assertion does not specify a series combination. Both statements are true, yet the explanation is missing. This pair matches B in the code above.

Now change the assertion to: "At a fixed potential difference, doubling resistance doubles current." Keep I = V/R as the reason. The assertion is false and the reason is true, matching D. Reusing a familiar formula does not make the assertion correct; the relationship must agree with it.

Use official answers to diagnose the mistake

Attempt the official sample questions before opening the matching marking scheme. Compare your chosen option with the official answer, then identify which decision went wrong. Did you misjudge the assertion, accept a false reason or mistake a related fact for an explanation?

Record the missed condition or concept, not just the correct letter. Rewrite a false statement so that it becomes scientifically correct. For a wrong explanation, name the link that would actually support the assertion. That gives your next revision task a clear purpose.

Use our Class 10 Science preparation guide for the wider revision plan. If the same concept keeps causing trouble, Science tuition can help you work through the reasoning rather than collect more answer keys.

Frequently asked questions

Does a true reason always explain a true assertion?

No. It must explain the particular assertion under its stated conditions, not merely be a correct fact from the same chapter.

Should I memorise the option letters?

Read the paper's option wording. The official sample paper provides a code, but another worksheet can use a different order.

What if both statements seem false?

Recheck the wording and source. Do not force the pair into an option whose meaning does not match your conclusion.

Will practising only assertion-reason questions cover Science?

No. The curriculum lists other question types too. Keep practising calculations, explanations, diagrams and case-based tasks alongside them.