Complete Mathematics Formulas for Class 6 to 10 – Free PDF Guide with Explanations

Complete Mathematics Formulas Guide for Class 6 to 10

Mathematics is built on fundamental formulas that serve as building blocks for advanced concepts. This comprehensive guide presents essential formulas from Class 6 through Class 10, organized systematically to help students master mathematical concepts with clarity and confidence.

Class 6 Mathematics Formulas

1. Number System

Concept Formula Explanation
Whole Numbers 0, 1, 2, 3, 4, … Numbers starting from zero with no fractions
Natural Numbers 1, 2, 3, 4, 5, … Counting numbers starting from 1
Integers …, -3, -2, -1, 0, 1, 2, 3, … Whole numbers including negative numbers
Even Numbers 2n (where n is any integer) Numbers divisible by 2
Odd Numbers 2n + 1 (where n is any integer) Numbers not divisible by 2

2. Basic Arithmetic Operations

Operation Formula Example
Addition a + b = sum 5 + 3 = 8
Subtraction a – b = difference 10 – 4 = 6
Multiplication a × b = product 6 × 7 = 42
Division a ÷ b = quotient 20 ÷ 4 = 5

3. Fractions

Concept Formula Explanation
Proper Fraction Numerator < Denominator Example: 3/5, 2/7
Improper Fraction Numerator ≥ Denominator Example: 7/3, 5/5
Mixed Fraction Whole number + Proper fraction Example: 2¹/₃
Addition of Fractions a/b + c/d = (ad + bc)/bd Cross multiply and add
Subtraction of Fractions a/b – c/d = (ad – bc)/bd Cross multiply and subtract
Multiplication of Fractions a/b × c/d = (a × c)/(b × d) Multiply numerators and denominators
Division of Fractions a/b ÷ c/d = a/b × d/c Multiply by reciprocal

4. Decimals

Concept Formula/Rule Example
Decimal to Fraction Place value method 0.5 = 5/10 = 1/2
Addition of Decimals Align decimal points 2.5 + 3.75 = 6.25
Multiplication of Decimals Multiply, count decimal places 2.5 × 0.4 = 1.00

5. Ratio and Proportion

Concept Formula Explanation
Ratio a : b or a/b Comparison of two quantities
Proportion a : b = c : d or a/b = c/d Equality of two ratios
Mean Proportional b² = ac (if a : b = b : c) b is mean proportional between a and c

6. Percentage

Concept Formula Explanation
Percentage (Value/Total) × 100% Parts per hundred
Converting Fraction to % (Fraction) × 100% Multiply fraction by 100
Converting % to Fraction %/100 Divide percentage by 100
Percentage Increase [(New – Old)/Old] × 100% Change relative to original
Percentage Decrease [(Old – New)/Old] × 100% Decrease relative to original

7. Geometry – Basic Shapes

Shape Perimeter Area
Square 4 × side = 4s side² = s²
Rectangle 2(length + breadth) = 2(l + b) length × breadth = l × b
Triangle a + b + c (sum of all sides) ½ × base × height = ½ × b × h
Circle 2πr (Circumference) πr²

8. Mensuration (Basic)

Concept Formula Units
Perimeter Sum of all sides cm, m, km
Area Space inside a shape cm², m², km²
Volume Space inside 3D object cm³, m³, l

Class 7 Mathematics Formulas

1. Integers

Operation Formula/Rule Example
Addition (same sign) Add and keep sign (-5) + (-3) = -8
Addition (different sign) Subtract and use larger sign (-5) + 3 = -2
Multiplication (+)(+) = +, (-)(-) = +, (+)(-) = – (-3) × (-4) = 12
Division Same rules as multiplication (-12) ÷ (-3) = 4

2. Exponents and Powers

Concept Formula Explanation
Power aⁿ = a × a × a … (n times) a is base, n is exponent
Product Rule aᵐ × aⁿ = aᵐ⁺ⁿ Add exponents with same base
Quotient Rule aᵐ ÷ aⁿ = aᵐ⁻ⁿ Subtract exponents with same base
Power of Power (aᵐ)ⁿ = aᵐⁿ Multiply exponents
Zero Exponent a⁰ = 1 Any number to power zero is 1
Negative Exponent a⁻ⁿ = 1/aⁿ Negative exponent means reciprocal

3. Algebraic Expressions

Identity Formula Expansion
Identity 1 (a + b)² a² + 2ab + b²
Identity 2 (a – b)² a² – 2ab + b²
Identity 3 (a + b)(a – b) a² – b²
Identity 4 (x + a)(x + b) x² + (a + b)x + ab

4. Simple Equations

Type Standard Form Solution Method
Linear Equation ax + b = c x = (c – b)/a
Transposition Move term across = sign Change sign when moving

5. Geometry – Lines and Angles

Concept Formula/Property Value
Straight Angle 180°
Right Angle 90°
Acute Angle Less than 90°
Obtuse Angle Between 90° and 180°
Complementary Angles a + b = 90° Sum is 90°
Supplementary Angles a + b = 180° Sum is 180°
Vertically Opposite Angles Equal ∠1 = ∠3, ∠2 = ∠4
Linear Pair a + b = 180° Adjacent angles on straight line

6. Triangle Properties

Property Formula Explanation
Sum of Angles ∠A + ∠B + ∠C = 180° Interior angles of triangle
Exterior Angle Exterior angle = Sum of opposite interior angles ∠ACD = ∠A + ∠B
Pythagorean Theorem a² + b² = c² For right-angled triangles

7. Perimeter and Area (Extended)

Shape Perimeter Area
Parallelogram 2(a + b) base × height = b × h
Rhombus 4 × side ½ × d₁ × d₂ (diagonals)
Trapezium a + b + c + d ½(a + b) × h

8. Simple Interest

Concept Formula Variables
Simple Interest SI = (P × R × T)/100 P = Principal, R = Rate, T = Time
Amount A = P + SI Total amount after interest
Principal P = (SI × 100)/(R × T) Original amount
Rate R = (SI × 100)/(P × T) Interest rate percentage
Time T = (SI × 100)/(P × R) Time period

Class 8 Mathematics Formulas

1. Rational Numbers

Property Formula Explanation
Rational Number p/q where q ≠ 0 Can be expressed as fraction
Addition a/b + c/d = (ad + bc)/bd Common denominator method
Multiplication a/b × c/d = ac/bd Multiply numerators and denominators
Additive Identity a/b + 0 = a/b Zero is additive identity
Multiplicative Identity a/b × 1 = a/b One is multiplicative identity

2. Squares and Square Roots

Concept Formula Example
Perfect Square 5² = 25
Square Root √n √25 = 5
Pythagorean Triplet a² + b² = c² 3, 4, 5 or 5, 12, 13
Property 1 √(a × b) = √a × √b √(4 × 9) = 2 × 3 = 6
Property 2 √(a/b) = √a/√b √(25/4) = 5/2

3. Cubes and Cube Roots

Concept Formula Example
Perfect Cube 3³ = 27
Cube Root ∛n ∛27 = 3
Sum of Cubes a³ + b³ = (a + b)(a² – ab + b²)
Difference of Cubes a³ – b³ = (a – b)(a² + ab + b²)

4. Algebraic Identities (Extended)

Identity Formula Expansion
Identity 5 (a + b)³ a³ + b³ + 3ab(a + b)
Identity 6 (a – b)³ a³ – b³ – 3ab(a – b)
Identity 7 a³ + b³ (a + b)(a² – ab + b²)
Identity 8 a³ – b³ (a – b)(a² + ab + b²)
Identity 9 (a + b + c)² a² + b² + c² + 2ab + 2bc + 2ca

5. Direct and Inverse Proportion

Type Formula Relationship
Direct Proportion x₁/y₁ = x₂/y₂ or x/y = k If x increases, y increases
Inverse Proportion x₁y₁ = x₂y₂ or xy = k If x increases, y decreases

6. Compound Interest

Concept Formula Explanation
Amount A = P(1 + R/100)ⁿ Compounded annually
Compound Interest CI = A – P Difference between amount and principal
Half-Yearly Compounding A = P(1 + R/200)²ⁿ Compounded twice a year
Quarterly Compounding A = P(1 + R/400)⁴ⁿ Compounded four times a year

7. Mensuration – Surface Areas and Volumes

Shape Total Surface Area Volume
Cube 6a²
Cuboid 2(lb + bh + hl) l × b × h
Cylinder 2πr(r + h) πr²h
Cone πr(r + l) where l = slant height ⅓πr²h
Sphere 4πr² ⁴⁄₃πr³
Hemisphere 3πr² ⅔πr³

8. Quadrilaterals

Shape Area Formula Special Properties
Square side² = a² All sides equal, all angles 90°
Rectangle length × breadth = l × b Opposite sides equal, all angles 90°
Parallelogram base × height = b × h Opposite sides parallel and equal
Rhombus ½ × d₁ × d₂ All sides equal, diagonals perpendicular
Trapezium ½(a + b) × h One pair of parallel sides

Class 9 Mathematics Formulas

1. Number System (Real Numbers)

Type Definition Examples
Natural Numbers (N) Counting numbers 1, 2, 3, 4, …
Whole Numbers (W) Natural numbers + 0 0, 1, 2, 3, …
Integers (Z) Whole numbers + negatives …, -2, -1, 0, 1, 2, …
Rational Numbers (Q) p/q form where q ≠ 0 2/3, -5/7, 0.5
Irrational Numbers Non-terminating, non-repeating √2, π, e
Real Numbers (R) Rational + Irrational All numbers on number line

2. Polynomials

Concept Formula Degree
Linear ax + b 1
Quadratic ax² + bx + c 2
Cubic ax³ + bx² + cx + d 3
Remainder Theorem p(a) = remainder when p(x) divided by (x – a)
Factor Theorem If p(a) = 0, then (x – a) is a factor

3. Algebraic Identities (Complete Set)

Identity Formula
1 (a + b)² = a² + 2ab + b²
2 (a – b)² = a² – 2ab + b²
3 a² – b² = (a + b)(a – b)
4 (a + b)³ = a³ + b³ + 3ab(a + b)
5 (a – b)³ = a³ – b³ – 3ab(a – b)
6 a³ + b³ = (a + b)(a² – ab + b²)
7 a³ – b³ = (a – b)(a² + ab + b²)
8 (x + a)(x + b) = x² + (a + b)x + ab
9 (a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ca

4. Linear Equations in Two Variables

Concept Formula Explanation
Standard Form ax + by + c = 0 Linear equation in two variables
Slope-Intercept Form y = mx + c m is slope, c is y-intercept
Point-Slope Form y – y₁ = m(x – x₁) Line through (x₁, y₁) with slope m
Two-Point Form (y – y₁)/(y₂ – y₁) = (x – x₁)/(x₂ – x₁) Line through two points

5. Coordinate Geometry

Concept Formula Explanation
Distance Formula d = √[(x₂ – x₁)² + (y₂ – y₁)²] Distance between two points
Section Formula x = (mx₂ + nx₁)/(m + n), y = (my₂ + ny₁)/(m + n) Point dividing line in ratio m:n
Midpoint Formula x = (x₁ + x₂)/2, y = (y₁ + y₂)/2 Midpoint of line segment
Area of Triangle ½ x₁(y₂ – y₃) + x₂(y₃ – y₁) + x₃(y₁ – y₂)

6. Euclid’s Geometry

Concept Statement
Euclid’s Division Lemma a = bq + r where 0 ≤ r < b
Euclid’s Algorithm HCF(a, b) = HCF(b, r) where a = bq + r

7. Triangles

Concept Formula/Theorem
Heron’s Formula Area = √[s(s-a)(s-b)(s-c)] where s = (a+b+c)/2
Congruency (SSS) Three sides equal
Congruency (SAS) Two sides and included angle equal
Congruency (ASA) Two angles and included side equal
Congruency (RHS) Right angle, hypotenuse, one side equal

8. Circles

Concept Formula Explanation
Circumference 2πr Perimeter of circle
Area πr² Space inside circle
Length of Arc (θ/360°) × 2πr θ is central angle
Area of Sector (θ/360°) × πr² Pie-shaped region
Area of Segment Area of sector – Area of triangle Region between chord and arc

9. Surface Areas and Volumes (Advanced)

Shape Curved Surface Area Total Surface Area Volume
Sphere 4πr² 4πr² ⁴⁄₃πr³
Hemisphere 2πr² 3πr² ⅔πr³
Cone πrl πr(l + r) ⅓πr²h
Cylinder 2πrh 2πr(r + h) πr²h
Frustum of Cone πl(r₁ + r₂) π[r₁² + r₂² + l(r₁ + r₂)] ⅓πh(r₁² + r₂² + r₁r₂)

10. Statistics

Concept Formula Explanation
Mean x̄ = Σx/n Average of observations
Median Middle value when arranged For odd n: (n+1)/2th term
Mode Most frequently occurring value Value with highest frequency
Range Maximum – Minimum Spread of data

11. Probability

Concept Formula Range
Probability P(E) = (Number of favorable outcomes)/(Total number of outcomes) 0 ≤ P(E) ≤ 1
Certain Event P(E) = 1 Always occurs
Impossible Event P(E) = 0 Never occurs
Complementary Events P(E) + P(not E) = 1 Sum equals 1

Class 10 Mathematics Formulas

1. Real Numbers (Advanced)

Concept Formula/Theorem Application
Fundamental Theorem of Arithmetic Every composite number can be expressed as product of primes uniquely Prime factorization
HCF × LCM HCF(a,b) × LCM(a,b) = a × b For two numbers
Rational Number Property p/q is terminating if q = 2ᵐ × 5ⁿ Decimal expansion

2. Quadratic Equations

Concept Formula Explanation
Standard Form ax² + bx + c = 0 a ≠ 0
Quadratic Formula x = [-b ± √(b² – 4ac)]/2a Solutions of quadratic equation
Discriminant D = b² – 4ac Determines nature of roots
Nature of Roots (D > 0) Two distinct real roots Unequal roots
Nature of Roots (D = 0) Two equal real roots Equal roots
Nature of Roots (D < 0) No real roots Complex roots
Sum of Roots α + β = -b/a Relationship between roots and coefficients
Product of Roots αβ = c/a Relationship between roots and coefficients
Forming Equation x² – (sum of roots)x + (product of roots) = 0 When roots are given

3. Arithmetic Progression (AP)

Concept Formula Variables
nth Term aₙ = a + (n-1)d a = first term, d = common difference
Sum of n Terms Sₙ = n/2[2a + (n-1)d] When first term and common difference known
Sum of n Terms (alternate) Sₙ = n/2(a + l) When first and last terms known
Common Difference d = a₂ – a₁ Difference between consecutive terms

4. Coordinate Geometry (Advanced)

Concept Formula Application
Distance Formula d = √[(x₂-x₁)² + (y₂-y₁)²] Distance between two points
Section Formula (Internal) P(x,y) = [(mx₂+nx₁)/(m+n), (my₂+ny₁)/(m+n)] Point dividing line internally in m:n
Section Formula (External) P(x,y) = [(mx₂-nx₁)/(m-n), (my₂-ny₁)/(m-n)] Point dividing line externally in m:n
Midpoint Formula M = [(x₁+x₂)/2, (y₁+y₂)/2] Middle point of line segment
Area of Triangle A = ½ x₁(y₂-y₃) + x₂(y₃-y₁) + x₃(y₁-y₂)
Collinearity Condition Area = 0 Three points are collinear if area = 0

5. Triangles (Similarity)

Concept Theorem/Criteria Statement
Basic Proportionality Theorem (Thales) If a line parallel to one side intersects other two sides It divides them proportionally
AA Similarity Two angles equal Triangles are similar
SSS Similarity Three sides proportional Triangles are similar
SAS Similarity Two sides proportional and included angle equal Triangles are similar
Pythagoras Theorem a² + b² = c² For right-angled triangles
Converse of Pythagoras If a² + b² = c², then triangle is right-angled

6. Circles (Advanced)

Concept Formula/Theorem Explanation
Length of Tangent √(d² – r²) d = distance from center to external point
Tangent Property Tangent ⊥ Radius at point of contact Perpendicular relationship
Two Tangents from External Point PA = PB Equal lengths from external point
Angle between Tangent and Chord Equal to angle in alternate segment Alternate segment theorem

7. Trigonometry

Ratio Formula Reciprocal
sine sin θ = Perpendicular/Hypotenuse cosec θ = 1/sin θ
cosine cos θ = Base/Hypotenuse sec θ = 1/cos θ
tangent tan θ = Perpendicular/Base cot θ = 1/tan θ

8. Trigonometric Identities

Identity Formula
Fundamental Identity sin²θ + cos²θ = 1
Identity 2 1 + tan²θ = sec²θ
Identity 3 1 + cot²θ = cosec²θ

9. Trigonometric Ratios of Standard Angles

Angle 30° 45° 60° 90°
sin θ 0 1/2 1/√2 √3/2 1
cos θ 1 √3/2 1/√2 1/2 0
tan θ 0 1/√3 1 √3
cot θ √3 1 1/√3 0
sec θ 1 2/√3 √2 2
cosec θ 2 √2 2/√3 1

10. Trigonometric Ratios of Complementary Angles

Identity Formula
sin(90° – θ) cos θ
cos(90° – θ) sin θ
tan(90° – θ) cot θ
cot(90° – θ) tan θ
sec(90° – θ) cosec θ
cosec(90° – θ) sec θ

11. Heights and Distances

Concept Definition Formula
Angle of Elevation Angle above horizontal tan θ = height/distance
Angle of Depression Angle below horizontal tan θ = height/distance

12. Statistics (Advanced)

Concept Formula For Grouped Data
Mean x̄ = Σfx/Σf Direct method
Mean (Assumed Mean) x̄ = a + Σfd/Σf Where d = x – a
Mean (Step Deviation) x̄ = a + (Σfu/Σf) × h Where u = (x-a)/h
Median l + [(n/2 – cf)/f] × h l = lower boundary, cf = cumulative frequency
Mode l + [(f₁-f₀)/(2f₁-f₀-f₂)] × h l = lower boundary of modal class

13. Probability (Advanced)

Concept Formula Explanation
Theoretical Probability P(E) = Number of favorable outcomes / Total outcomes Based on theory
Experimental Probability P(E) = Number of times event occurred / Total trials Based on experiment
Sum of Probabilities P(E) + P(Ē) = 1 Complementary events

14. Surface Areas and Volumes (Combinations)

Concept Formula Application
Combination of Solids Total Surface Area = Sum – Common Area When two solids joined
Volume of Combination Total Volume = Sum of individual volumes Adding volumes
Conversion 1 m³ = 1000 liters Volume to capacity

Important Constants

Constant Symbol Value (approx.)
Pi π 3.14159 or 22/7
Euler’s Number e 2.71828
Golden Ratio φ 1.61803

Units and Conversions

Quantity SI Unit Common Conversions
Length meter (m) 1 km = 1000 m, 1 m = 100 cm
Area square meter (m²) 1 hectare = 10,000 m²
Volume cubic meter (m³) 1 m³ = 1000 liters
Time second (s) 1 hour = 3600 s
Speed meter/second (m/s) 1 km/h = 5/18 m/s

Conclusion

This comprehensive guide covers all essential mathematics formulas from Class 6 to Class 10, organized systematically for easy reference. Regular practice with these formulas, combined with conceptual understanding, will build a strong mathematical foundation. Remember that formulas are tools understanding when and how to apply them is as important as memorizing them.

For best results, students should practice problems from textbooks, solve worksheets, and attempt sample papers regularly. This guide serves as a quick reference during revision and exam preparation.

Note: While this guide is comprehensive, students should always refer to their NCERT textbooks and consult teachers for detailed explanations and additional practice problems.

FAQs on Maths Formulas for Class 6 to 10

Q. What are the most important maths formulas for Class 6?

The most important maths formulas for Class 6 include:

Basic Arithmetic & Number System:

  • Even numbers: 2n (where n is any integer)
  • Odd numbers: 2n + 1

Fractions & Decimals:

  • Addition of fractions: a/b + c/d = (ad + bc)/bd
  • Multiplication of fractions: a/b × c/d = (a × c)/(b × d)

Ratio & Percentage:

  • Percentage = (Value/Total) × 100%
  • Ratio: a : b or a/b

Geometry – Area & Perimeter:

  • Square: Perimeter = 4s, Area = s²
  • Rectangle: Perimeter = 2(l + b), Area = l × b
  • Triangle: Area = ½ × base × height
  • Circle: Circumference = 2πr, Area = πr²

Q. How can I remember all maths formulas easily?

Here are proven techniques to memorize maths formulas effectively:

1. Understanding over Memorization:

  • Learn how formulas are derived rather than rote learning
  • Understand the logic behind each formula

2. Practice Daily:

  • Solve 5-10 problems daily using different formulas
  • Application helps retention better than reading

3. Create Visual Aids:

  • Make colorful formula charts for your study room
  • Use flashcards for quick revision
  • Draw diagrams for geometry formulas

4. Use Mnemonics:

  • For trigonometry: “Some People Have Curly Brown Hair Through Proper Brushing” (sin = P/H, cos = B/H, tan = P/B)
  • Create your own memory tricks for complex formulas

5. Group Similar Formulas:

  • Organize by topic (algebra, geometry, mensuration)
  • Study related formulas together

6. Regular Revision:

  • Review formulas weekly, not just before exams
  • Use spaced repetition technique

7. Teach Others:

  • Explain formulas to classmates or family members
  • Teaching reinforces your own understanding

8. Make Formula Sheets:

  • Create separate sheets for each chapter
  • Keep them handy during homework and revision

Q. Where can I download maths formulas PDF for Class 6 to 10?

You can access maths formulas PDFs from several reliable sources:

Official & Educational Resources:

  1. NCERT Official Website (www.ncert.nic.in)
    • Free textbooks with all formulas
    • Chapter-wise PDFs available
    • Most authentic source for CBSE students
  2. School Websites
    • Many schools provide formula sheets
    • Check your school’s academic resources section
  3. Educational Platforms:
    • BYJU’S, Khan Academy, Vedantu
    • Offer free downloadable formula PDFs
    • Often include solved examples
  4. Government Educational Portals:
    • DIKSHA platform
    • State education board websites

What to Look For in a Good Formula PDF:

  • Organized by class and chapter
  • Clear explanations with examples
  • Includes all NCERT topics
  • Easy-to-read formatting
  • Printable format

Q. What is the difference between Class 9 and Class 10 maths formulas?

Class 9 and Class 10 maths formulas differ significantly in complexity and application:

Class 9 Maths Formulas:

Foundation Building:

  • Introduction to coordinate geometry (distance formula, section formula)
  • Basic polynomial identities
  • Heron’s formula for triangle area
  • Simple surface area and volume formulas
  • Basic trigonometric ratios (sin, cos, tan)
  • Introduction to statistics (mean, median, mode)
  • Basic probability concepts

Class 10 Maths Formulas:

Advanced Applications:

  • Quadratic Equations: Complete formula including discriminant (D = b² – 4ac)
  • Arithmetic Progressions: nth term and sum formulas
  • Advanced Coordinate Geometry: Section formula (internal & external division)
  • Trigonometry: All six ratios, identities (sin²θ + cos²θ = 1), complementary angles
  • Standard trigonometric values: For 0°, 30°, 45°, 60°, 90°
  • Advanced Statistics: Formulas for grouped data, median, mode calculations
  • Circle Theorems: Tangent properties, length of tangent formula
  • Similar Triangles: Proportionality theorems

Differences:

Aspect Class 9 Class 10
Complexity Introductory level Advanced, board exam level
Trigonometry Basic 3 ratios All 6 ratios + identities
Algebra Simple polynomials Quadratic equations
Statistics Ungrouped data Grouped data with frequency
Application Conceptual understanding Problem-solving for exams

Q. Which algebraic identities are most important for board exams?

The following algebraic identities are crucial for board exams (Classes 9-10) and appear frequently:

Top 8 Essential Identities:

1. Square of Sum:

  • (a + b)² = a² + 2ab + b²
  • Most frequently used in expansions and factorization

2. Square of Difference:

  • (a – b)² = a² – 2ab + b²
  • Common in simplification problems

3. Difference of Squares:

  • a² – b² = (a + b)(a – b)
  • Used extensively in factorization

4. Cube of Sum:

  • (a + b)³ = a³ + b³ + 3ab(a + b)
  • Alternative form: a³ + 3a²b + 3ab² + b³

5. Cube of Difference:

  • (a – b)³ = a³ – b³ – 3ab(a – b)
  • Alternative form: a³ – 3a²b + 3ab² – b³

6. Sum of Cubes:

  • a³ + b³ = (a + b)(a² – ab + b²)
  • Important for factorization questions

7. Difference of Cubes:

  • a³ – b³ = (a – b)(a² + ab + b²)
  • Frequently asked in board exams

8. Square of Trinomial:

  • (a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ca
  • Appears in complex algebraic problems

Q. How to prepare mensuration formulas for Class 8 to 10?

A comprehensive strategy to master mensuration formulas:

Step 1: Understand the Basics (Class 8 Level)

2D Shapes:

  • Square, Rectangle, Triangle, Circle
  • Parallelogram, Rhombus, Trapezium
  • Focus on area and perimeter

3D Shapes:

  • Cube, Cuboid, Cylinder
  • Learn surface area (curved, total) and volume

Step 2: Organized Formula Learning

Create a Formula Chart with 4 Columns:

Shape Curved/Lateral Surface Area Total Surface Area Volume
Cube 6a²
Cuboid 2h(l+b) 2(lb+bh+hl) l×b×h
Cylinder 2πrh 2πr(r+h) πr²h
Cone πrl πr(l+r) ⅓πr²h
Sphere 4πr² 4πr² ⁴⁄₃πr³
Hemisphere 2πr² 3πr² ⅔πr³

Step 3: Advanced Concepts (Class 9-10)

Combination of Solids:

  • Hemisphere on cylinder
  • Cone attached to cylinder
  • Formula: Total SA = Sum of individual SA – Common area

Frustum of Cone (Class 10):

  • Volume = ⅓πh(r₁² + r₂² + r₁r₂)
  • Curved Surface Area = πl(r₁ + r₂)

Step 4: Effective Practice Strategy

Visual Learning:

  • Draw 3D shapes while writing formulas
  • Label all dimensions clearly
  • Understand which measurement is what (radius, height, slant height)

Smart Practice Tips:

  1. Solve 5 problems daily from each shape type
  2. Identify the shape in word problems carefully
  3. Make unit conversions confidently (cm to m, m³ to liters)
  4. Check units in your answer (area = cm², volume = cm³)

Common Mistakes to Avoid:

  • Confusing radius with diameter
  • Using wrong formula (curved vs. total surface area)
  • Forgetting π value (use 22/7 or 3.14 as specified)
  • Not converting units before calculation

Revision Technique:

  • Week 1: 2D shapes
  • Week 2: Basic 3D shapes (cube, cuboid, cylinder)
  • Week 3: Advanced 3D shapes (cone, sphere)
  • Week 4: Combination problems and frustum

Q. What are the basic trigonometry formulas for Class 10?

Complete guide to Class 10 trigonometry formulas:

Part 1: Basic Trigonometric Ratios

In a Right-Angled Triangle:

  • sin θ = Perpendicular/Hypotenuse (P/H)
  • cos θ = Base/Hypotenuse (B/H)
  • tan θ = Perpendicular/Base (P/B)

Reciprocal Ratios:

  • cosec θ = 1/sin θ = H/P
  • sec θ = 1/cos θ = H/B
  • cot θ = 1/tan θ = B/P

Part 2: Fundamental Trigonometric Identities

Three Main Identities (Must Memorize):

  1. sin²θ + cos²θ = 1
    • Most important identity
    • Used in 40% of trigonometry problems
  2. 1 + tan²θ = sec²θ
    • Derived from Identity 1
  3. 1 + cot²θ = cosec²θ
    • Also derived from Identity 1

Part 3: Standard Angles Values (Crucial for Board Exams)

Angle sin θ cos θ tan θ cot θ sec θ cosec θ
0 1 0 1
30° 1/2 √3/2 1/√3 √3 2/√3 2
45° 1/√2 1/√2 1 1 √2 √2
60° √3/2 1/2 √3 1/√3 2 2/√3
90° 1 0 0 1

Memory Pattern for sin:

  • √0/2, √1/2, √2/2, √3/2, √4/2 (for 0°, 30°, 45°, 60°, 90°)
  • For cos: Reverse the pattern

Part 4: Complementary Angle Formulas

When two angles add up to 90° (complementary):

  • sin(90° – θ) = cos θ
  • cos(90° – θ) = sin θ
  • tan(90° – θ) = cot θ
  • cot(90° – θ) = tan θ
  • sec(90° – θ) = cosec θ
  • cosec(90° – θ) = sec θ

Part 5: Quotient Identities

  • tan θ = sin θ/cos θ
  • cot θ = cos θ/sin θ

Q. What is the quadratic formula and when should I use it?

Complete guide to the quadratic formula – one of the most important formulas in Class 10:

The Quadratic Formula:

For any quadratic equation ax² + bx + c = 0 (where a ≠ 0):

x = [-b ± √(b² – 4ac)] / 2a

This formula gives you both roots (solutions) of the quadratic equation.

Understanding the Components:

The Discriminant (D):

  • D = b² – 4ac
  • This determines the nature of roots

Nature of Roots Based on Discriminant:

Discriminant Value Nature of Roots Example
D > 0 Two distinct real roots x² – 5x + 6 = 0 (D = 1)
D = 0 Two equal real roots x² – 4x + 4 = 0 (D = 0)
D < 0 No real roots (imaginary) x² + x + 1 = 0 (D = -3)

When to Use the Quadratic Formula:

Use When:

  1. Factorization is difficult or impossible
    • Example: x² + 5x + 3 = 0 (doesn’t factor easily)
  2. Asked specifically to use formula method
    • Board exams often ask “solve by quadratic formula”
  3. Finding decimal/exact roots
    • When precise values are needed
  4. Coefficients are large numbers
    • Example: 7x² + 15x + 2 = 0
  5. When time is limited
    • Formula method is faster than trial-and-error

Don’t Use When:

  1. Simple factorization is possible
    • Example: x² – 5x + 6 = 0 → (x-2)(x-3) = 0
  2. Completing the square is easier
    • Some problems are designed for this method
  3. Equation can be simplified first
    • 2x² – 8x + 6 = 0 → x² – 4x + 3 = 0

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