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Examiner Insights · CBSE Class 10 Maths

Where CBSE Class 10 Maths students lose marks — and exactly what to do about it

CBSE does not publish examiner reports. This page uses CBSE's official unit weights and marking-scheme conventions, plus public analyses of common errors (each linked). The mistakes are well documented but not ranked by CBSE itself.

  • 7sources checked
  • 7syllabus topics weighted
  • 8mistakes catalogued
  • 5focus areas for 2027 board exams
What to focus on for 2027 board examsTop 8 mistakesGet the one-page PDF

Summaries are in our own words with links to the originals. Predictions are informed guesses, not a guarantee.

Ranked for 2027 board exams (Feb–Mar 2027)

What to focus on for 2027 board exams (Feb–Mar 2027)

Based on the 2025-26 curriculum weights; check the 2026-27 curriculum when CBSE publishes it. Ranked by us from the official marks per unit and how often each error comes up in the sources below; CBSE publishes no ranking of its own.

Informed prediction, not a guarantee: any topic on the specification can be examined.

  1. 1

    Algebra: quadratics, AP, linear equations, polynomials

    20 of 80 marks — the largest unit — with step marking rewarding full working.

    High confidenceCBSE unit weights 2025-26
    LearnPractise Class 10 chaptersMistake: Skipping steps the marking scheme rewardsMistake: Arithmetic progressions
  2. 2

    Triangles and circles (proofs and theorems)

    15 marks; written proofs need every reason.

    High confidenceCBSE unit weights
    LearnPractise Class 10 chapters
  3. 3

    Trigonometric identities and heights and distances

    12 marks; identity proofs are a recurring weak area.

    Medium confidenceCBSE unit weightsSecondary analyses
    LearnPractise Class 10 chaptersMistake: Trigonometric identities
  4. 4

    Grouped-data statistics and probability

    11 marks; median/mode formula and sample-space errors.

    High confidenceCBSE unit weights
    LearnPractise Class 10 chaptersMistake: StatisticsMistake: Probability
  5. 5

    Surface areas, volumes and areas related to circles

    10 marks; units and π.

    High confidenceCBSE unit weights
    LearnPractise Class 10 chaptersMistake: Mensuration
Mistakes library

The 8 mistakes that cost the most marks

Ordered by how often and how widely they were reported. The first 5 are free in full; Essentials unlocks the fix and a worked example for every other one.

#1Skipping steps the marking scheme rewards

What goes wrong: CBSE marking schemes award marks for each step, and secondary analyses of board results list skipped working as a leading cause of lost marks.

Fix: Show the formula, the substitution and the simplification on separate lines, even when you can do it mentally.

Worked example (our own): Solve 2x² − 7x + 3 = 0 using the quadratic formula.

Loses marks

  1. x = 3 or x = ½

Earns the marks

  1. a = 2, b = −7, c = 3
  2. D = b² − 4ac = 49 − 24 = 25
  3. x = (7 ± √25)/(2 × 2) = (7 ± 5)/4
  4. x = 3 or x = ½

Why: CBSE marking schemes give marks for steps (identifying a, b, c, the discriminant, substitution, answer). A bare answer can lose most of them.

Sources: CBSE sample question papers and marking schemes (Mathematics); Physics Wallah — Class 10 Maths common mistakes to avoid; SuperTutor — Class 10 board exam: common mistakes that cost marks

Learn: AlgebraPractise this

#2Sign and arithmetic slips

What goes wrong: The most frequently cited error in public analyses: a misplaced sign or decimal changes the whole answer.

Fix: Bracket negatives when substituting; re-check each line; leave a few minutes to recheck calculations.

Worked example (our own): Find the value of 3x² − 2x when x = −3.

Loses marks

  1. 3(−3)² − 2(−3) = −27 − 6 = −33

Earns the marks

  1. 3(−3)² − 2(−3) = 3(9) + 6
  2. = 27 + 6 = 33

Why: (−3)² = +9, and subtracting a negative adds. Bracket every negative number you substitute.

Sources: Physics Wallah — Class 10 Maths common mistakes to avoid; SuperTutor — Class 10 board exam: common mistakes that cost marks

Learn: AlgebraPractise this

#3Trigonometric identities: proofs without clear steps

What goes wrong: Proofs jump from one side to the answer or manipulate both sides at once, which does not show the identity.

Fix: Work from one side to the other, name each identity used, end with "= RHS".

Worked example (our own): Prove that (1 − cos²θ)(1 + cot²θ) = 1.

Loses marks

  1. sin²θ × cosec²θ = 1

Earns the marks

  1. LHS = (1 − cos²θ)(1 + cot²θ)
  2. = sin²θ × cosec²θ (using sin²θ + cos²θ = 1 and 1 + cot²θ = cosec²θ)
  3. = sin²θ × 1/sin²θ = 1 = RHS

Why: Start from one side, name each identity you use, and finish with "= RHS".

Sources: Physics Wallah — Class 10 Maths common mistakes to avoid; CBSE sample question papers and marking schemes (Mathematics)

Learn: TrigonometryPractise this

#4Mensuration: units, π and squaring the radius

What goes wrong: Answers lose marks for wrong units (cm² for a volume), a different value of π from the one given, and forgetting to square r.

Fix: Write the formula, square r, use the π given, and finish with the right unit.

Worked example (our own): Find the volume of a cone of radius 7 cm and height 12 cm. (Use π = 22/7.)

Loses marks

  1. ⅓ × 3.14 × 7 × 12 = 87.9 cm²

Earns the marks

  1. V = ⅓πr²h = ⅓ × 22/7 × 7² × 12
  2. = ⅓ × 154 × 12 = 616 cm³

Why: Square the radius, use the value of π the question gives, and use cubic units for volume.

Sources: Physics Wallah — Class 10 Maths common mistakes to avoid; SuperTutor — Class 10 board exam: common mistakes that cost marks

Learn: MensurationPractise this

#5Statistics: median class versus modal class

What goes wrong: In grouped-data questions the median class is chosen by highest frequency, or the wrong cumulative frequency is used in the formula.

Fix: Median class: first cf ≥ n/2. Modal class: highest frequency. Write the formula and each value before substituting.

Worked example (our own): For grouped data with n = 50, the cumulative frequencies are 8, 22, 30, 45, 50 for the classes 0–10, 10–20, 20–30, 30–40, 40–50. Which is the median class?

Loses marks

  1. The class with the highest frequency (15), 30–40 (that is the modal class, not the median class)

Earns the marks

  1. n/2 = 25
  2. The first cumulative frequency ≥ 25 is 30, so the median class is 20–30 (frequency 30 − 22 = 8)
  3. Median = l + ((n/2 − cf)/f) × h = 20 + ((25 − 22)/8) × 10 = 23.75

Why: The median class comes from the cumulative frequency (first cf ≥ n/2); the modal class comes from the largest frequency. Use the cf of the class BEFORE the median class in the formula.

Sources: CBSE sample question papers and marking schemes (Mathematics); Physics Wallah — Class 10 Maths common mistakes to avoid

Learn: Statistics and probabilityPractise this
Topic weight

Marks per unit (CBSE curriculum)

CBSE fixes the marks for each unit in the curriculum, so every board paper follows these weights. Total: 80 marks.

Algebra20 marks
Geometry (triangles, circles)15 marks
Trigonometry12 marks
Statistics and probability11 marks
Mensuration10 marks
Number systems6 marks
Coordinate geometry6 marks

Confidence: high. Source: CBSE Secondary / Senior Secondary Curriculum 2025-26: Mathematics (unit-wise marks).

Essentials

Your mistakes vs this course's mark-loss hot-spots

We set the topics in your mistake notebook and your practice scores against this page's mistakes library and focus list, and rank where they overlap, with a practice link for each.

Free account: how many of your notebook entries match, and the top one. Essentials: the full ranked list, your focus areas and your risk list.

Also on your dashboard.

Free download

Top 8 mistakes that cost marks in CBSE Class 10 Maths

A one-page PDF of the 8 most common mark-losing mistakes and how to avoid them. Print it and stick it inside your revision folder.

We'll also send occasional revision tips. Unsubscribe any time; we never share your address.

Sources

Where this comes from

CBSE does not publish examiner reports. This page uses CBSE's official unit weights and marking-scheme conventions, plus public analyses of common errors (each linked). The mistakes are well documented but not ranked by CBSE itself.

FAQ

What are the most common mistakes in CBSE Class 10 Maths?

The most repeated points are: Skipping steps the marking scheme rewards; Sign and arithmetic slips; Trigonometric identities. Each one on this page has the fix and, where free, a worked example showing the wrong and right method.

Which CBSE Class 10 Maths topics come up most?

In the material we analysed, the biggest areas were Algebra (20 marks), Geometry (triangles, circles) (15 marks), Trigonometry (12 marks).

Is this a prediction of the 2027 board exams (Feb–Mar 2027) paper?

No one outside the exam board knows what will be on the next paper. The "focus" list is an informed prediction from how often topics appeared and how weakly they were answered; it is not a guarantee, so revise the whole specification.

Where does this information come from?

CBSE does not publish examiner reports. This page uses CBSE's official unit weights and marking-scheme conventions, plus public analyses of common errors (each linked). The mistakes are well documented but not ranked by CBSE itself.

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