Hg
Name: Class 9 STICK TO YOUR WALL IN STUDY AREA
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The Hg Classes (8
th
to 12
th
) By: Er Hershit Goyal (B.Tech. IIT BHU), 134-SF, Woodstock Floors, Nirvana Country, Sector 50, GURUGRAM +91 9599697178.
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Mensuration Formulae (2D shapes)
SQUARE:
s = length of a side
Perimeter = 4s
Area = s
2
RECTANGLE:
l = length
w = width or breadth
Perimeter = 2 (l + w)
Area = l x w
TRIANGLE:
a, b, c = sides, b = base, h = height
Perimeter = a + b + c
s = Semi-Perimeter =
Area =
b h
=
PARALLELOGRAM:
b = base, h = height,
a = other side
Perimeter = 2(a + b)
Area = b h
RHOMBUS:
l = side; d
1
, d
2
= diagonals
Perimeter = 4 l = 2
Area =
d
1
d
2
EQUILATERAL TRIANGLE:
a = side
Perimeter = 3a
Height =
a
Area =
a
2
CIRCLE:
r = radius
d = diameter
Diameter = 2r
Perimeter = 2πr
Area = πr
2
RING or ANNULUS:
r = inner radius
R = outer radius
Width = R – r
Area = π (R
2
– r
2
)
TRAPEZIUM:
Perimeter = a + b + c + d
Area =
(sum of || sides) h
=
(a + b) h
