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CBSE Class 8 Maths Important Formulas

Many students consider mathematics as a scary subject and math formulas are often difficult to remember when you don’t understand them well. The negative approach towards any subjects will make a student reluctant to study that particular subject.Usually students feel jittery during the exam time and they fail to give their best shot. To make things easier and guide through different concepts in Maths, we will discuss the important math formulas for class 8 here.

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 Algebraic  Expansions:

    1. (a + b)2 = a2 + 2ab + b2
    2. (a – b) = a2 – 2ab + b2
    3. (a + b) (a – b) = a2 – b2
    4. (x + a)(x + b) = x2 + (a + b)x + ab
    5.  (x + a)(x – b) = x2 + (a – b)x – ab
    6.  (x – a)(x + b) = x2 + (b – a)x – ab
    7.  (x – a)(x – b)  = x2 – (a + b)x + ab
    8.  (a + b)3 = a3 + b3 + 3ab(a + b)
    9.  (a – b)3  = a3 – b3 – 3ab (a – b)
   10. (x + y + z)2 = x2 + y2 + z2 + 2xy + 2yz + 2xz
   11. (x + y – z)2  = x2 + y2 + z2 + 2xy – 2yz – 2xz
   12. (x – y + z)2 = x2 + y2 + z2 – 2xy – 2yz + 2xz

   13. (x – y – z)2  = x2 + y2 + z2 – 2xy + 2yz – 2xz


Temperature Conversions :

ºC  = 5959  ( ºF – 32 )  ºF = 9595  ( ºC + 32 )

Simple Interest  = PTR100PTR100

Pythagorean Theorem:

a+ b2  = c2

Pythagorean Theorem Figure

Laws of Exponents
Product Law:  am*an = am+n
Quotient Law:  =  aman=amnaman=am−n, if m>n
=  1anm1an−m ,if n>m

 Power law:  (am)n = amn

Geometrical Formula:

Sl.No Figure Formula for surface area Formula for volume
 1  Rectangular Prism
 SA = 2ab+2bc+2ca  sq. units
where a, b,c are the sides of the cube.
 V = abc  cubic units
 2  Cylinder
 SA = 2πrh  sq. units
 TSA =  2πr(h+r)  sq. units
 r =radius of the cylinder
 h – height of the cylinder
V = πr2h  cubic units
 3  Cube
 SA = 6a2  sq. units
 a = sides of the cube
 V = a3    cubic units
 4  Sphere
 SA = 4πr2  sq. units
 r = radius of the sphere
 V = 4343πr  cubic units
 5  Ellipsoid
 SA = 4π[(apbp+apcp+bpcp)3]1p4π[(apbp+apcp+bpcp)3]1p
p = 1.6075
a, b, c are semi axis of ellipsoid
 V = 4343 π r1,r2,r3  cubic units
 6  Cone  CSA = πr1 sq.units  V = 1313πr2h   cubic units
 7  Pyramid
 SA = a+1212*p*l
 p = perimeter of pyramid
 l = slant height
 a = area of the base of the pyramid
 V = 1313*a*h  cubic units
 8  Torus
 SA =  π2 * (R2 – r2)
 R:Outer Radius
 r: Inner Radius
 V = 1414π3 (r1+r2) (r1-r2)2  cubic units
 9  Hemisphere
 CSA = 2πr2
 TSA = 3πr
 r = radius
 V = 2323 πr3   cubic units
 10  Triangle
 SA = s(sa)(sb)(sc)‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√s(s−a)(s−b)(s−c)
 where s is the perimeter of the triangle
 a, b, c are the sides of the triangle
 11  Rectangle
 A = l*w
 L = length
 w = width
 12  Triangle
 A = 1212bh
 b = base  h = height
 13  Trapezoid  A = 1212 h (b1+b2)
 14  Parallelogram  A = bh
 15  Circle  A = πr2   r = radius