Page 1 - 11.3-Lesson Notes-Area of Triangle and Triangle as parts of Rectangle Ch-11

SAI International School

CLASS-VII
Mathematics
CHAPTER-8: Perimeter and Area

LESSON NOTES- 3

SUBTOPIC: Area of Triangle, Triangle as a part of rectangle

Area of Triangle: Let ABCD is a parallelogram. Cut the parallelogram along its
diagonal to get two triangles as shown in the figure.

 The base and the height of the triangle are the same as the base and the
height of the parallelogram, respectively.
 Now, we will find that the sum of the areas of both the triangles is equal to the
area of the parallelogram.

 Now,Area of each triangle = x(Area of parallelogram)

= x (base x height)

= x (b x h)

=

NOTE:All the congruent triangles are equal in area but the triangles equal in area
need not be congruent.

Triangles as Parts of Rectangles:Let us take a rectangle and cut the
rectangle along its diagonal to get two triangles as shown in the figure.