Parallelograms and Rectangles on Same Base and between Same Parallels

Parallelograms and rectangles on same base and between same parallels are equal in area.

In the adjoining figure, parallelogram ABCD and rectangle ABEF are on the same base BC and between the same parallels AB and l.

Parallelograms and Rectangles on Same Base and between Same Parallels






Therefore, area of parallelogram ABCD = Area of rectangle ABEF

                                                   = AB × AF

AF is also the altitude of the parallelogram.

Hence, area of the parallelogram = base × height

                                            = AB × AF


Solved examples for the rectangles and parallelograms on same base and between same parallels:

1. Parallelogram ABCD and rectangle ABFE have some base AB, and the length and breadth of the rectangle are as 7 cm and 4 cm. find the area of the parallelogram.

Parallelograms and Rectangles






Solution:

Length of rectangle = 7 cm

Breadth of rectangle = 4 cm

Therefore, area of rectangle = 7 × 4 cm2

                                       = 28 cm2

Since, rectangle ABFE and parallelogram ABCD are on the same base AB.

Therefore, area of parallelogram = Area of rectangle

Therefore, area of parallelogram ABCD = 28 cm2

2. In the adjacent figure ABCD is a parallelogram and EFCD is a rectangle.

Parallelograms and Rectangle

Also, AL ⊥ DC. Prove that

(a) Area (ABCD) = Area (EFCD)

(b) Area (ABCD) = DC × AL

Solution:

(a) As a rectangle is also a parallelogram,

Therefore, Area (ABCD) = Area (EFCD)

(b) From above result,

Area (ABCD) = DC × FC (Area of the rectangle = length × breadth)    ……………… (i)

As           AL ⊥ DC, therefore, AFCL is also a rectangle

So,          AL ⊥ FC             ……………… (ii)

Therefore, from (i) and (ii) we get

Area (ABCD) = DC × AL

From the above result we see that, area of a parallelogram is the product of it’s any side and the corresponding altitude.

Figure on Same Base and between Same Parallels

Parallelograms on Same Base and between Same Parallels

Parallelograms and Rectangles on Same Base and between Same Parallels

Triangle and Parallelogram on Same Base and between Same Parallels

Triangle on Same Base and between Same Parallels





8th Grade Math Practice

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