RS Aggarwal & V Aggarwal - Mathematics

Book: RS Aggarwal & V Aggarwal - Mathematics

Chapter: 7. Areas

Subject: Mathematics - Class 9th

Q. No. 22 of Exercise 7A

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22

Find the area of a parallelogram ABCD in which AB = 28cm, BC = 26cm and diagonal AC = 30 cm.

Let the sides of the triangle ABC be:


a = 26 cm


b = 30 cm


And


c = 28 cm


Let us find out the value of s


We know that,


s =


=


=


= 42 cm


We know that,


Area of triangle ABC =


=


=


=


=


= 14 × 3 × 4 × 2


= 336 cm2


We know that,


In a parallelogram, the diagonal divides the parallelogram in two equal area


Therefore,


Area of quadrilateral ABCD = Area of triangle ABC + Area of triangle ACD


= Area of triangle ABC × 2


= 336 × 2


= 672 cm2


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