# 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

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 = 4343πr3   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 = 3πr2   r = radius V = 2323 πr3   cubic units 10 Triangle SA = s(s−a)(s−b)(s−c)‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾√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