# 9th Class Mathematics Areas of Parallelograms and Triangles Area of Parallelograms and Triangles

Area of Parallelograms and Triangles

Category : 9th Class

Areas of Parallelograms and Triangles

• A polygonal region is the union of a polygon and it’s interior. For e.g., the union of a triangle and its interior is called the triangular region.

• Every polygonal region has area. Area of a figure is a number associated with the part of the plane enclosed by that figure.

• Two congruent figures have equal areas but figures with equal areas need not be congruent.

• If ABCD is a rectangle with AB = $l$ m and BC = b m, then the area of the rectangular region ABCD is$lb\text{ }sq.\text{ }m\text{ }or\text{ l}b\text{ }{{m}^{2}}$.

• If A and B are two regions having at the most a line segment common between them two, then the area of their combined region S is equal to the sum of their areas taken separately. i.e, ar (S) = ar (A) +ar (B).

• The area of a parallelogram is the product of any of its sides and the corresponding altitude.

• 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 the same line parallel to the base.

• A diagonal of a parallelogram divides it into two triangles of equal areas.

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

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

• Parallelograms on equal bases and between the same parallel lines are equal in area.

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

• Triangles on the same base and between the same parallel lines are equal in area.
• Two triangles having the same base (or equal bases) and equal areas lie between the same parallel lines.
• If a triangle and a parallelogram are on the same base and between the same parallel lines, then the area of the triangle is equal to half that of the parallelogram.

• The area of a trapezium is half the product of its height and the sum of the parallel sides.

• Triangles with equal areas and having one side of one triangle, equal to one side of the other, have their corresponding altitudes equal.

• A rectangle and a parallelogram on the same base and between the same parallels have the same area.

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

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##### Notes - Area of Parallelograms and Triangles

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