UPSC NDA Math Model Paper 10

Given: L1:y=3x,L2:,y=6x and L3:y=9
Let A be the point of intersection of L1 and L2. Then co-ordinates of point A is: (0, 0)
Let B be the point of intersection of L2 and L3. Then co-ordinates of point B is: (3 / 2, 9)
Let C be the point of intersection of L3 and L1.Then co-ordinates of point C is: (3, 9)
As, we know that if A(x1,y1),B(x2,y2) and C(x3,y3)be the vertices of a ΔABC. Then Area of ΔABC=

1

2

×|

x1	y1	1
x2	y2	1
x3	y3	1

|
⇒ Area of ΔABC=

1

2

×|

0	0	1
3 2	9	1
3	9	1

| =|

1

2

×1×(

27

2

−27)|=

27

4

sq. units