Chap 11
SOME IMPORTANT FACTS
1. PERIMETER : The sum of lengths of all
sides of a plane figure is called the perimeter of the figure.
2. Area : The measurement of the region
enclosed by plane figure is called the area of the plane figure.
3. Area of Rectangle : Length X Breadth
Length
= Area / Breadth
; Breadth = Area / length
4. Area of four walls : = [
2 ( length + Breadth ) x height )
5. Area of Square = (side )2 =
(diagonal )2 /2
6. Side of Square = √Area
7. Area of Parallelogram =
Base x Height
Base =
Area / Height ; Height =
Area / Base
8. Area of Quadrilateral = Diogonal
x ( Sum of perpendicular from opposite
vertices on it )
9. Area of Rhombus = product
of Diagonals/2
10. Area of Triangle = (
Base x Height ) / 2
11. Area of Trapezium = (
Sum of parallel sides ) X ( distance between them )
2
12.
The
Circumference /Perimeter of a circle
= 2 πr
13. Area of a circle of radius r = πr2
14. Cuboid
; ii) Volume
of a Cuboid = Length x Breadth x
Height =
( lbh ) Cu. Units
i) Total Surface Area of a Cuboid = 2 (
lb + bh + lh ) sq. units
iii) Lateral Surface Area of a Cuboid = [ 2 ( l + b ) x h ] Sq. units
15. Cube
; i) Volume
of a Cube = (Edge )3
= a3 Cu. Units
i) Total Surface Area of a Cube = 6 a2
sq. units
iii) Lateral Surface Area of a Cube = 4a2
Sq. units
16.
Cylinder
; suppose a cylinder of Height ‘h’ and
radius ‘ r’
a.
Volume = πr2h Cu. Units
b.
Lateral
Surface Area = 2 πrh sq. Units
c.
Total surface Area = (2 πrh + 2πr2 ) sq. Units
17.
i)
1 cm3 = 1
ml
ii) 1 liter = 1000 cm3
i)
1
m3 = 1000000 cm3 =
1000 liters
