Question: If $ A,(-,5,7), $ $ B,(-,4,-5), $ $ C,(-1,-,6) $ and $ D,(4,5) $ are the vertices of a quadrilateral, then find the area of the quadrilateral ABCD.
Options:
A) 72 sq units
B) 80 sq units
C) 90 sq units
D) 92 sq units
Show Answer
Answer:
Correct Answer: A
Solution:
- By joining B and D, we get two triangles $ \Delta ABD $ and $ \Delta BCD. $
Given, $ x _1=-5, $ $ =x _2=-4, $ $ x _3=4, $ $ y _1=7 $
$ y _2=-5 $ and $ y _3=5 $
Area of
$ \Delta ABD=| \frac{1}{2}[x _1(y _2-y _3)+x _2(y _3-y _1)+x _3(y _1-y _2)], | $ $ =\frac{1}{2}[-5(-,5-5)+(-4)(5-7)+4(7+5)] $
$ =\frac{1}{2}[50+8+48]=\frac{106}{2}=53squnits $
Now, in $ \Delta BCD $
$ x _1=-4, $ $ x _2=-1, $ $ x _3=4, $
$ y _1=-5, $ $ y _2=-6 $ and $ y _3=5 $
Area of
$ \Delta BCD=| \frac{1}{2}[-4(-6-5)-1(5+5)+4(-5+6)]| . $
$ =\frac{1}{2}(44-10+4) $
$ =\frac{1}{2}\times 38=19 $ sq units
$ \therefore $ Area of quadrilateral $ \Delta BCD $
= Area of $ \Delta ABD $ + Area of $ \Delta BCD $
$ =53+19=72 $ sq units