Page 114 - Revised Maths Wisdom Class - 6

112 MATHS

Area of Triangle

If you want to know the area of triangle with the help of rectangle then first of all draw a rectangle on a piece of
paper and also draw its diagonals. Cut the rectangle along that diagonal and get two triangles.
Now, according to figure A B
Area of rectangle ABCD = Area of triangle (ABD) + Area of triangle (DCB)

Area of rectangle = 2 × Area of triangle
Note : These two triangles over lap each other exactly D C

So, Area of ∆ ABD = Area of ∆ DCB
Now, Calculate the area of triangle using the square grid, if each square has side of 1 cm

Alternative Approach

We know that
1
Area of triangle = × Base × height
2
In this triangle ⇐ Base = 4, height = 3
1
Area of triangle = × Base × height
3 complete square and 3 more than half square 2
1
So, area = (3 × 1) cm + (3 × 1) cm = 3 cm + 3 cm = 6 cm . = × 4 × 3 = 6 cm 2
2
2
2
2
2
2
ILLUSTRATIONS
Example 1: Find the area of the figure given below:
Solution: No. of complete squares in figure ( f ) = 4

No. of half squares (h) = 6 and
No of more than half enclosed squares (m) = 0

Thus, total area = 4 + (6 ÷ 2) = 4 + 3 = 7 sq. cm
Example 2: Find the area of the following figures by counting squares: