Let's solve this step by step.

a) Work out the area of the whole rectangle:

• The dimensions of the rectangle are given as 8 cm (length) and 3 cm (width).
• The formula for the area of a rectangle is:

$\text{Area of rectangle} = \text{Length} \times \text{Width}$

Substituting the values:

$\text{Area of rectangle} = 8 \, \text{cm} \times 3 \, \text{cm} = 24 \, \text{cm}^2$

b) Work out the area of the dotted, yellow triangle:

• The base of the triangle is 8 cm (same as the length of the rectangle).
• The height of the triangle is 3 cm (same as the width of the rectangle).
• The formula for the area of a triangle is:

$\text{Area of triangle} = \frac{1}{2} \times \text{Base} \times \text{Height}$

Substituting the values:

$\text{Area of triangle} = \frac{1}{2} \times 8 \, \text{cm} \times 3 \, \text{cm} = 12 \, \text{cm}^2$

Summary:

• The area of the rectangle is 24 cm².
• The area of the dotted, yellow triangle is 12 cm².

Do you have any questions or need further details?

Here are 5 related questions:

1. How do you find the area of a parallelogram?
2. What is the relationship between a triangle and a rectangle when they share the same base and height?
3. Can the formula for the area of a triangle be applied to any triangle? Why or why not?
4. What would be the area if the base or height of the triangle was doubled?
5. How does the concept of symmetry help in understanding areas of geometric shapes?

Tip: When solving geometry problems, always check if any symmetry or common dimensions can simplify your calculations.