If the difference between the sides of a right angled triangle is 3 cm and its area is 54 cm²; find its perimeter.

The area of the given figure is :

1. AC x BD

2. $\dfrac{1}{2}\times AC \times BD$

3. $\dfrac{1}{2}\times AB \times BD$

4. $\dfrac{1}{2}\times (AD + BC) \times BD$

A square DEFG of side 8 cm is inscribed in a rectangle of adjacent sides 20 cm and 16 cm as shown in the figure.

The area of the shaded portion is :

1. 64 cm²

2. 128 cm²

3. 256 cm²

4. 320 cm²

The perimeter of a square is 72 cm, its area is :

1. $900\sqrt{2} \text{ cm}^2$

2. $30\sqrt{3} \text{ cm}^2$

3. 324 cm²

4. 356 cm²