To calculate the area of the given shape, we can split it into two parts:

1. A rectangle with a width of 4 cm and a height of 20 cm.
2. A right triangle with a base of $9 \, \text{cm} - 4 \, \text{cm} = 5 \, \text{cm}$ and a height of 2 cm.

Step-by-step solution:

1. Calculate the area of the rectangle:

$\text{Area of rectangle} = \text{width} \times \text{height} = 4 \, \text{cm} \times 20 \, \text{cm} = 80 \, \text{cm}^2$

2. Calculate the area of the triangle:

$\text{Area of triangle} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 5 \, \text{cm} \times 2 \, \text{cm} = 5 \, \text{cm}^2$

3. Add the two areas:

$\text{Total area} = \text{Area of rectangle} + \text{Area of triangle} = 80 \, \text{cm}^2 + 5 \, \text{cm}^2 = 85 \, \text{cm}^2$

Final Answer:

The total area of the shape is 85 cm².

Would you like a breakdown of this solution, or do you have additional questions?

Here are 5 questions that expand on this topic:

1. What are other ways to split composite shapes into simpler ones for area calculations?
2. How does the formula for the area of a triangle relate to that of a rectangle?
3. Can you calculate the area of the same shape if the dimensions were doubled?
4. What is the significance of the base and height alignment in triangles when calculating areas?
5. How could we find the perimeter of this shape?

Tip: Always ensure that all measurements are in the same unit when calculating areas or other geometrical properties.