How do you find the surface area of a flat shape?

Hint: Flat shapes mean the shapes that exist only in 2-dimensions, that is, they do not have height, they have only length and breadth. We know some of the basic 2-dimensional shapes that are rectangle, square, triangle, circle, etc. and we also know the formula for calculating their area. With a similar approach, we can find the area of any 2-dimensional figure.

Complete step-by-step solution:
A square is a 2-dimensional figure that has 4 sides, each of the sides is perpendicular to the other side and all the sides are equal to each other. The area of a square is given by the formula –
$area = {(side)^2}$
A rectangle is also a 2-dimensional figure having 4 sides perpendicular to each other. Opposite sides of a rectangle are equal while adjacent sides are unequal to each other. The area of a rectangle is given by –
$area = length \times breadth$
A triangle is a 2-dimensional figure having 3 sides, its area is given by the formula –
$area = \dfrac{1}{2} \times base \times altitude$
These are some of the basic shapes, area.

Note: The surface area of a shape is defined as the sum of the areas of all the flat surfaces in a figure, since a flat shape has only one flat surface, so its area is calculated by a simple formula. There are two kinds of shapes in geometry that are 3-dimensional and 2-dimensional. The 2-dimensional shapes are also known as flat shapes. 3-dimensional shapes have length, breadth and height while 2-dimensional shapes have only length and breadth.