CBSE Class 10 board exam: the questions that keep coming back
Concepts repeat in board papers far more than exact questions do. These are the topics that kept appearing in recent papers, each explained in a one-minute animated lesson, in English and Hindi, with the exam-style answer written out.
Science: Physics
Light, the human eye, electricity and magnetism keep returning as 1-mark facts, reasoning questions and numericals.
- Why does myopia need a concave lens? — Class 10Defects of vision: about 6 questions in 2023-2025
- Reflection vs Refraction — why a straw looks bent in waterRefraction of light: about 5 questions in 2023-2025
- Why does a concave mirror converge but a concave lens diverge? — Class 10
- Why does a dentist use a concave mirror? — Class 10
- Why can a convex mirror never form a real image? — Class 10 Physics
- Ohm's Law — why more resistance means less currentOhm's law and resistance: asked in several years
- Why do wires get hot when too many appliances run? — Class 10
- Why does a fuse wire have low melting point and high resistance? — Class 10
- Why is the earth wire important for safety? — Class 10 Physics
Science: Chemistry
Chemical reactions, acids and bases, metals and carbon compounds. Equations and reasons are asked again and again.
- Oxidation vs Reduction — redox without a trace of oxygenOxidation and reduction: about 7 questions in 2023-2025
- How does common salt give baking soda, washing soda and bleaching powder? — Class 10Chemicals from common salt: about 6 questions in 2023-2025
- Acids vs Bases vs Salts — why 'strong' and 'concentrated' are not the same wordAcids and bases: pH, reactions with metals, about 5 questions
- Why does an acid's pH move toward 7 when diluted? — Class 10
- Why add acid to water and never water to acid? — Class 10 Chemistry
- Why does hard water not lather with soap? — Class 10
- Why is rusting of iron a chemical change? — Class 10
- Is carbon dioxide ionic or covalent? — Class 10
- Ionic vs Covalent Bond — sharing is not the same as giving away
Science: Biology
Heredity, life processes and ecosystems carry a large share of the Biology marks and repeat the most.
- Why does the F2 generation show a 3 : 1 ratio? — Class 10Mendel's rules of inheritance: about 8 questions in 2023-2025
- Genotype vs Phenotype — can you tell someone's genotype just by looking at their phenotype?
- Aerobic vs Anaerobic Respiration — do human muscles ever respire without oxygen?Respiration: about 8 questions in 2023-2025
- Why do muscles cramp after sprinting? — Class 10
- Food Chain vs Food Web — is a food web just a bigger food chain?Food chains and webs: about 6 questions in 2023-2025
- Why does only 10% of energy pass to the next trophic level? — Class 10
- Reflex Action vs Voluntary Action — does your brain decide to pull your hand off a hot pan?
- Xylem vs Phloem — does phloem always carry food downward?
- Why does a wilted plant stand up again after watering? — Class 10
Mathematics
The paper is 80 marks: Algebra 20, Geometry 15, Trigonometry 12, Statistics and Probability 11, Mensuration 10, Number Systems 6, Coordinate Geometry 6. Proofs and "show that" questions repeat.
- Why is √2 irrational? The proof — Class 10Proving a number irrational: a repeated Real Numbers question
- Why does HCF × LCM equal the product of two numbers?
- Why is the sum of zeroes −b/a and the product c/a? — Class 10
- When do two linear equations have no solution? — Class 10
- Why does a quadratic have at most two real roots? — Class 10
- Why is the distance formula just Pythagoras? — Class 10
- Why are two equal angles enough to prove triangles similar (AA)? — Class 10
- Why is a tangent perpendicular to the radius? — Class 10
- Why is the angle of depression equal to the angle of elevation? — Class 10Heights and distances: a repeated Trigonometry application
- Why is probability always between 0 and 1? — Class 10
- Mean vs Median vs Mode — why one outlier can lie to you
How to use this page
Pick your weakest subject, open a lesson, and answer the quick check at the end. Each lesson ends with the way to write the answer in the exam, and a note on the common mistake.
Counts come from published analyses of the 2023-2025 papers and are a guide to what to revise, not a prediction.
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Common questions
- Which topics are repeated most in the CBSE Class 10 board exam?
- In Science, analysis of the 2023-2025 papers shows heredity (Mendel's rules), respiration, oxidation and reduction, food chains, defects of vision and chemicals from common salt among the most repeated. In Maths, irrationality proofs, zeroes and coefficients, linear equations, similarity, heights and distances, and probability keep returning.
- Will these exact questions come in my board exam?
- No one can promise that. Concepts repeat much more than exact wording. Understanding why an answer is true lets you handle a changed question, which is why each lesson explains the reason, not just the answer.
- How are the Class 10 board papers structured?
- Each main subject has an 80-mark theory paper (3 hours) and 20 marks of internal assessment. The papers include a large share of competency-based and case-based questions along with objective and short and long answers.