In the adjoining figure, the area of triangle ABC is

1. 15 sq. units

2. 10 sq. units

3. 7.5 sq. units

4. 2.5 sq. units

The points A(9, 0), B(9, 6), C(-9, 6) and D(-9, 0) are the vertices of a

1. rectangle

2. square

3. rhombus

4. trapezium

Three vertices of a rectangle are A(2, -1), B(2, 7) and C(4, 7). Plot these points on a graph and hence use it to find the co-ordinates of the fourth vertex D. Also find the co-ordinates of

(i) the mid-point of BC

(ii) the mid-point of CD

(iii) the point of intersection of the diagonals.

What is the area of the rectangle ?