In symbols, A^ =^21 bh where ‘b’ is the base and ‘h’ is the height of the right angle
triangle.
The idea may be explained to the child orally again through paper folding or through
cutouts.
- Perimeter of a right angle triangle
The perimeter of a right angle triangle is the sum of its three sides.
Eg. : Find the perimeter of the right triangle whose sides are 3 cm, 4 cm and 5cm
respectively.
Perimeter of the right triangle = Sum of its three sides
= 3 + 4 + 5
= 12 cm
As the perimeter of the triangle is equal to the sum of its sides, the procedure followed
in finding the perimeter of a square and the rectangle may be followed in the case of
the triangle also.
- Area of four walls
Area of four walls = Perimeter of the room × height
In symbols, A = ph, where ‘p’ is the perimeter of the room and ‘h’ is its height.
Eg. : The length, width and height of a room are 10 m, 6 m and 4m respectively.
Find the area of its four walls.
Given, length (l) = 10 m, width (b) = 6m and height (h) = 4m
Therefore, perimeter of the room, p = 2 (l + b)
= 2 (10+ 6)
= 2 (16)
= 32 m
