00
:
Q 24. The perimeter of the following shape
(in meters) is
5 m
2 m
8 m
14 m
A) 34
B) 44
C) 48
D) 46
Answers
Answer:
Explanation:
• Rectangle
(a) Area = length × breadth
(b) Perimeter = 2 (length + breadth)
(c) Diagonal = ( )( ) 2 2 length + breadth
• Square
(a) Area = (side)2
(b) Perimeter = 4 × side
(c) Diagonal = 2 × side
• Triangle with base (b) and altitude (h)
Area =
1
2
× ×b h
• Triangle with sides as a, b, c
(i) Semi-perimeter = 2
abc
s
+ + =
(ii) Area = ss a s b s c ( )( )( ) ––– (Heron’s Formula)
• Isosceles triangle, with base a and equal sides b
HERON’S FORMULA
CHAPTER 12
16/04/18 16/04/18
Area of isosceles triangle = 2 2 4 –
4
a b a
• Equilateral triangle with side a
Area = 3 2
4
a
• Parallelogram with base b and altitude h
Area = bh
• Rhombus with diagonals d1
and d2
(a) Area = 1 2
1
2
d d ×
(b) Perimeter = 2 2
1 2 2 d d +
• Trapezium with parallel sides a and b, and the distance between two parallel
sides as h.
Area =
1
2 (a + b) × h
• Regular hexagon with side a
Area = 6 × Area of an equilateral triangle with side a
= 3 2 6
4
× a = 3 2 3
2
a