CBSE Grade 8 Mathematics Exam Survival Guide

Window: Annual Exam | Units: Algebra, Geometry, Mensuration, Data, Number Systems

Must-do topics (with how-to + examples)

• Rational Numbers → Closure, additive inverse, distributive property.
  Ex: (2/3 + 4/5) × 1/2 → add first → multiply → simplify.
• Exponents & Powers → Laws of exponents, scientific notation.
  Ex: 2⁵ ÷ 2³ = 2² = 4.
• Algebraic Identities → (a+b)², (a−b)², a²−b², (x+a)(x+b).
  Ex: (x+5)(x−5) = x²−25.
• Factorisation → Common factor, regrouping, identities.
• Linear Equations in One Variable → Transpose terms step by step.
  Ex: 2x−7=13 → 2x=20 → x=10.
• Mensuration → SA & volume of cube, cuboid, cylinder, cone, sphere.
  Ex: Volume of cone = ⅓πr²h.
• Data Handling → Bar graph, pie chart, probability (favourable ÷ total).
• Geometry → Quadrilaterals, polygons, parallel lines, angle sum property.

Top traps (avoid)

• Forgetting to write units in area/volume.
• Applying wrong identity (e.g., confusing (a+b)² with a²+b²).
• Probability >1 or <0 (impossible!).
• Linear equation step skips → careless errors.

Time split

Algebra + Equations 40% | Geometry/Mensuration 40% | Data 20%
Do 1-mark Qs first → long SA/volumes mid → data last.

Last-48h checklist

• 20 Qs identities/factorisation.
• 10 mensuration sums (cone, cylinder, sphere).
• Revise probability basics + 1 pie chart.
• One 3-hour past paper.

Quick facts / formulas

• (a+b)² = a²+2ab+b² | (a−b)² = a²−2ab+b² | a²−b² = (a+b)(a−b)
• SA sphere = 4πr² | Vol sphere = 4/3πr³
• Probability = favourable ÷ total

Speed tactics

• Write formula first → substitute → solve → box answer.
• Check denominators in fractions (don’t drop).
• Draw diagrams to visualise SA/volumes.

Exam-day mini-plan

• Start with algebra Qs → mensuration → geometry proofs → data last.
• Keep 15 min for unit/sign checks.