Math Formulas for Class 8 – Complete List with Examples and PDF
Mathematics in Class 8 serves as a vital bridge between basic arithmetic and the more complex concepts of high school math. Mastering math formulas for class 8 is not just about memorization; it is about building a toolkit that allows students to solve problems with speed and precision. Whether you are dealing with rational numbers, algebraic expressions, or complex 3D shapes, having a comprehensive class 8 formula sheet is essential for academic success.
In this guide, we provide an exhaustive list of important formulas for class 8 categorized by topic, accompanied by solved examples and a downloadable PDF to help you ace your exams.
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Why Math Formulas are Important for Class 8 Students
- Speed and Efficiency: Formulas allow students to skip long-winded logical deductions and reach the answer directly.
- Accuracy: Using a standard formula minimizes the chance of manual errors during complex steps.
- Foundation for Competitive Exams: Many concepts in Class 8 appear in Olympiads and entrance exams. A strong grasp of class 8 maths formulas provides a significant competitive edge.
- Problem-Solving Skills: Understanding how a formula is derived helps in visualizing the relationship between different mathematical quantities.
1. Basic Arithmetic and Number System Formulas
Arithmetic in Class 8 covers Rational Numbers, Percentages, and Averages. These are the building blocks for daily life calculations and higher mathematics.
Basic Operations – Properties
- Commutative Property: a + b = b + a and a × b = b × a
- Associative Property: a + (b + c) = (a + b) + c
- Distributive Property: a(b + c) = ab + ac
Percentage and Average Formulas
| Concept | Formula |
|---|---|
| Percentage | Percentage = (Obtained Value / Total Value) × 100 |
| Percentage Change | Change % = ((New Value – Original Value) / Original Value) × 100 |
| Average (Mean) | Average = (Sum of all observations) / (Number of observations) |
2. Algebra Formulas
Algebraic identities are one of the most important parts of any math formulas for class 8 list. These identities help in simplifying expressions and solving equations quickly.
Standard Algebraic Identities
| Identity | Formula |
|---|---|
| Square of a Sum | (a + b)² = a² + 2ab + b² |
| Square of a Difference | (a – b)² = a² – 2ab + b² |
| Difference of Two Squares | a² – b² = (a + b)(a – b) |
| Product of Binomials | (x + a)(x + b) = x² + (a + b)x + ab |
3. Geometry and Mensuration Formulas
Geometry in Class 8 involves finding the perimeter and area of 2D shapes, as well as the surface area and volume of 3D objects.
2D Shapes (Area and Perimeter)
| Shape | Perimeter Formula | Area Formula |
|---|---|---|
| Square | 4 × side | side² |
| Rectangle | 2(L + W) | L × W |
| Triangle | a + b + c | ½ × base × height |
| Circle | 2πr | πr² |
| Trapezium | Sum of all sides | ½ × (a + b) × h |
4. Comparing Quantities: Profit, Loss, and Interest
- Profit: SP – CP
- Loss: CP – SP
- Simple Interest (SI): SI = (P × R × T) / 100
- Compound Interest (CI): A = P(1 + R/100)n and CI = A – P
5. Exponents and Powers
| Law | Formula |
|---|---|
| Multiplication Law | am × an = am+n |
| Division Law | am / an = am−n |
| Power of a Power | (am)n = amn |
| Zero Exponent | a0 = 1 (a ≠ 0) |
| Negative Exponent | a−m = 1 / am |
Solved Examples Using Class 8 Maths Formulas
Example 1: Algebra
Expand (2x + 3y)².
Using (a + b)² = a² + 2ab + b² with a = 2x, b = 3y:
= (2x)² + 2(2x)(3y) + (3y)² = 4x² + 12xy + 9y².
Example 2: Geometry (Area of Rectangle)
Length 15 m, width 10 m → Area = L × W = 15 × 10 = 150 m².
Example 3: Percentage
Scores 450 out of 500 → Percentage = (450/500)×100 = 90%.
Example 4: Average
Numbers 10,20,30,40 → Sum = 100, count = 4 → Average = 25.
(Click to download: complete formula sheet with all topics for quick revision)
Tips to Remember Math Formulas for Class 8
- Understand the Logic: Derive (a+b)² by multiplying (a+b)(a+b) to see why it works.
- Practice Daily: Solve at least 5 problems using different formulas every day.
- Flashcards: Write the name of the shape or identity on one side and the formula on the other.
- Visualize: For geometry, draw the shape and label the dimensions.
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FAQs about Class 8 Math Formulas
1. What are the most important algebra formulas for Class 8?
The three primary identities are (a+b)², (a–b)², and a²–b². They form the basis for most algebraic problems.
2. How do I calculate Compound Interest in Class 8?
Use A = P(1 + R/100)n then subtract Principal to get CI = A – P.
3. What is the difference between Area and Perimeter?
Perimeter is the boundary length; Area is the space inside (square units).
4. How can I memorize formulas effectively?
Regular problem-solving and writing formulas down repeatedly helps build muscle memory.
5. Are these formulas sufficient for Class 8 board exams?
Yes, this list covers Arithmetic, Algebra, Mensuration, and Data Handling as per most curricula.
6. What is the formula for the area of a Trapezium?
½ × (sum of parallel sides) × height.
7. Why do we use 'π' in circle formulas?
π (Pi) is the ratio of circumference to diameter (~3.14159 or 22/7).
8. What is the distributive property?
a(b + c) = ab + ac.
9. Can I find volume formulas in Class 8?
Yes: Cube (s³), Cuboid (L×W×H), Cylinder (πr²h).
10. Is there a simple way to remember laws of exponents?
When multiplying same base: add exponents. Dividing: subtract exponents.