Let's solve the problem step by step.

Part a) Work out the area of the whole rectangle.

The dimensions of the rectangle are given as:

• Length = 8 cm
• Width = 3 cm

The area of a rectangle is calculated using the formula: $\text{Area of rectangle} = \text{Length} \times \text{Width}$

Substituting the given values: $\text{Area of rectangle} = 8 \, \text{cm} \times 3 \, \text{cm} = 24 \, \text{cm}^2$

So, the area of the whole rectangle is 24 cm².

Part b) Use your answer to part a) to help you work out the area of the dotted yellow triangle.

The dotted yellow triangle is a right-angled triangle, and its base and height can be taken from the rectangle:

• Base = 8 cm (same as the length of the rectangle)
• Height = 3 cm (same as the width of the rectangle)

The area of a triangle is calculated using the formula: $\text{Area of triangle} = \frac{1}{2} \times \text{Base} \times \text{Height}$

Substituting the values: $\text{Area of triangle} = \frac{1}{2} \times 8 \, \text{cm} \times 3 \, \text{cm} = \frac{1}{2} \times 24 \, \text{cm}^2 = 12 \, \text{cm}^2$

Thus, the area of the dotted yellow triangle is 12 cm².

Would you like any further clarification or details on these calculations?

Here are some related questions for practice:

1. What would the area of the rectangle be if its length was doubled?
2. How would you calculate the perimeter of the rectangle?
3. If the triangle’s height was 6 cm, what would its new area be?
4. What is the relationship between the areas of the rectangle and the triangle?
5. How would you calculate the diagonal length of the rectangle?

Tip: Always remember to check if all units are consistent before applying formulas to avoid calculation errors.