Home » CBSE Class 9 Maths Notes for Chapter 9 Areas of Parallelograms and Triangles

# CBSE Class 9 Maths Notes for Chapter 9 Areas of Parallelograms and Triangles

CHAPTER 9 AREAS OF PARALLELOGRAMS AND TRIANGLES

• Area of a figure is a number (in some unit) associated with the part of the plane enclosed by that figure.

• Two congruent figures have equal areas but the converse need not be true.

• If a planar region formed by a figure T is made up of two non-overlapping planar regions formed by figures P and Q, then area (T) = area (P) + area(Q), where area (X) denotes the area of figure X.

• Two figures are said to be on the same base and between the same parallels, if they have a common base (side) and the vertices, (or the vertex) opposite to the common base of each figure lie on a line parallel to the base.

• Parallelograms on the same base (or equal bases) and between the same parallels are equal in area.

• Area of a parallelogram is the product of its base and the corresponding altitude.

• Parallelograms on the same base (or equal bases) and having equal areas lie between the same parallels.

• If a parallelogram and a triangle are on the same base and between the same parallels, then area of the triangle is half the area of the parallelogram.

• Triangles on the same base (or equal bases) and between the same parallels are equal in area.

• Area of a triangle is half the product of its base and the corresponding altitude.

• Triangles on the same base (or equal bases) and having equal areas lie between the same parallels.

• A median of a triangle divides it into two triangles of equal areas.