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Class 8 Maths Formulas & Calculators

Browse free Class 8 mathematics formulas, solved examples and working calculators. Indian school maths concepts.

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Percentage

p=\frac{\text{part}}{\text{whole}}\times100

Express part of a whole out of one hundred.

Open calculator →Arithmetic

Percent of a Number

x\times\frac{p}{100}

Calculate a given percentage of a number.

Open calculator →Arithmetic

Ratio Simplification

a:b=\frac{a}{g}:\frac{b}{g}

Divide both terms by their greatest common divisor.

Open calculator →Arithmetic

HCF of Two Integers

\operatorname{HCF}(a,b)

Greatest positive integer dividing both integers.

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LCM of Two Integers

\operatorname{LCM}(a,b)=\frac{|ab|}{\operatorname{HCF}(a,b)}

Smallest nonnegative common multiple; both nonzero for positive LCM.

Open calculator →Geometry

Triangle Area

A=\frac12 bh

Half the product of base and perpendicular height.

Open calculator →Geometry

Parallelogram Area

\(A=bh\)

Base times perpendicular height.

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Circle Circumference

C=2\pi r

Distance around a circle of radius r.

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Circle Area

A=\pi r^2

Area inside a circle of radius r.

Open calculator →Arithmetic

Simple Interest

SI=\frac{PRT}{100}

Interest on principal P at annual rate R% for T years.

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Profit

\text{Profit}=SP-CP

Selling price minus cost price.

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Profit Percentage

\frac{SP-CP}{CP}\times100

Profit relative to cost price; CP must be positive.

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Discount

D=\frac{MP\times d}{100}

Discount on marked price at rate d%.

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Speed

v=\frac{d}{t}

Speed equals distance divided by elapsed time.

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Distance

\(d=vt\)

Distance at constant speed.

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Time

t=\frac{d}{v}

Travel time at constant nonzero speed.

Open calculator →Geometry

Cube Volume

\(V=a^3\)

Volume of a cube with side a.

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Cuboid Volume

\(V=lbh\)

Volume of a rectangular box.

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Cube Total Surface Area

\(S=6a^2\)

Six equal square faces.

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Cuboid Total Surface Area

\(S=2(lb+bh+hl)\)

Sum of areas of six rectangular faces.

Open calculator →Arithmetic

Compound Amount

A=P(1+\frac{r}{100})^t

Amount with annual compounding.

Open calculator →Algebra

Square of a Sum

\((a+b)^2=a^2+2ab+b^2\)

Expand the square of a binomial.

Learn formula →Algebra

Square of a Difference

\((a-b)^2=a^2-2ab+b^2\)

Expand the square of a difference.

Learn formula →Algebra

Difference of Squares

\(a^2-b^2=(a-b)(a+b)\)

Factor a difference of two squares.

Learn formula →Algebra

Product Identity

\((x+a)(x+b)=x^2+(a+b)x+ab\)

Expand two linear factors.

Learn formula →Algebra

Linear Equation

ax+b=c\Rightarrow x=\frac{c-b}{a}

Solve an equation in one variable when a ≠ 0.

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Exponent Product

a^m a^n=a^{m+n}

Same base: add exponents.

Learn formula →Algebra

Exponent Quotient

\frac{a^m}{a^n}=a^{m-n}

Same nonzero base: subtract exponents.

Learn formula →Algebra

Power of a Power

(a^m)^n=a^{mn}

Multiply exponents.

Learn formula →Geometry

Trapezium Area

A=\frac12(a+b)h

Average of parallel sides times perpendicular height.

Open calculator →Geometry

Rhombus Area

A=\frac12d_1d_2

Half product of diagonals.

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Cylinder Volume

V=\pi r^2h

Circular base area times height.

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Cylinder Curved Surface Area

CSA=2\pi rh

Area of curved part of a right circular cylinder.

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Cone Volume

V=\frac13\pi r^2h

One third of matching cylinder volume.

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Sphere Volume

V=\frac43\pi r^3

Volume of a sphere.

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Sphere Surface Area

S=4\pi r^2

Surface area of a sphere.

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Pythagoras Theorem

\(a^2+b^2=c^2\)

Right triangle legs a,b and hypotenuse c.

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Heron Formula

A=\sqrt{s(s-a)(s-b)(s-c)}

Triangle area from sides; s=(a+b+c)/2.

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