Question:
The area of quadrilateral ABCD in the given figure is
(a) 57 cm2
(b) 108 cm2
(c) 114 cm2
(d) 195 cm2
Solution:
(c) $114 \mathrm{~cm}^{2}$
ar (quad. ABCD) = ar (∆ ABC) + ar (∆ ACD)
In right angle triangle ACD, we have:
$A C=\sqrt{\left(17^{2}-8^{2}\right)}=\sqrt{225}=15 \mathrm{~cm}$
In right angle triangle ABC, we have:
$B C=\sqrt{\left(15^{2}-9^{2}\right)}=\sqrt{144}=12 \mathrm{~cm}$
Now, we have the following:
$\operatorname{ar}(\Delta A B C)=\frac{1}{2} \times 12 \times 9=54 \mathrm{~cm}^{2}$
$\operatorname{ar}(\Delta A D C)=\frac{1}{2} \times 15 \times 8=60 \mathrm{~cm}^{2}$
$\operatorname{ar}($ quad $. A B C D)=54+60=114 \mathrm{~cm}^{2}$