Page 151 - Maths Skills - 7

Perimeter and Area 149

MIND MAP

Perimeter Perimeter and Area

Circle
Features � Diameter (d) = 2 × radius (r) Circumference
� It is like a fence around a shape � Circumference = 2pr A d B
� It denotes the total length of the � Area of circle = pr 2 Centre O r
shape’s boundary
� It is 1-D � Area of ring = pR – pr 2
2
� It express in meter or cm etc. = p(R – r ) R
2
2
= p(R + r) (R – r) O r

Formulae

Triangle side (1) + side (2) + side (3) Area Rememberable Things
Equilateral triangle 3 × side � 1 acre = 4046.85 m 2
Rectangle 2 (length + breadth) � 1 hectare = 10000 m 2
Square 4 × side

Features
� It is like a covered space of the 2-D boundary
� It is 2-D
2
� It express in meter or cm etc.
2

Formulae
Rectangle length × breadth E H
Square (side) 2 A D
1
Triangle × base × height
2
Equilateral Triangle 4 3 × (side) 2 B C
Parallelogram base × corresponding height F G
Area of rectangular path = area of rectangle EFGH – area of rectangle ABCD