Area Figures
1. **Problem 7:** Find the area of figure ABCDEFGH.
Given:
- AC = HF = $\sqrt{5^2 - 4^2} = \sqrt{25 - 16} = \sqrt{9} = 3$ cm.
- Area = area of rectangle ADEH + 2 × area of triangle ABC.
Step 1: Calculate area of rectangle ADEH.
- Rectangle ADEH has length DE = 8 cm (given) and height AH = 5 cm.
- Area = length × height = $8 \times 5 = 40$ cm$^2$.
Step 2: Calculate area of triangle ABC.
- Triangle ABC is right-angled with base BC = 4 cm and height AB = 5 cm.
- Area = $\frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 4 \times 5 = 10$ cm$^2$.
Step 3: Calculate total area.
- Total area = area of rectangle + 2 × area of triangle
- $= 40 + 2 \times 10 = 40 + 20 = 60$ cm$^2$.
2. **Problem 8:** Find the area of a regular hexagon ABCDEF with each side 13 cm and height 23 cm.
Given:
- Height AL + LM + DM = 23 cm,
- LM = BC = 13 cm (side length),
- AL = DM = x.
- So: $x + 13 + x = 23 \Rightarrow 2x = 10 \Rightarrow x = 5$ cm.
Step 1: Find length FL.
- Using Pythagoras theorem for triangle AFL:
$$FL^2 = AF^2 - AL^2 = 13^2 - 5^2 = 169 - 25 = 144$$
- So, $FL = \sqrt{144} = 12$ cm.
Step 2: Area of trapezium ADEF.
- Bases AF and DE are both equal to 13 cm (side of hexagon), height FL = 12 cm.
- Area of trapezium $= \frac{1}{2} \times (AF + DE) \times FL = \frac{1}{2} \times (13 + 13) \times 12 = \frac{1}{2} \times 26 \times 12 = 156$ cm$^2$.
Step 3: Total area of hexagon.
- Hexagon = 2 × area of trapezium ADEF
- Total area $= 2 \times 156 = 312$ cm$^2$.
**Final answers:**
- Question 7 area = $60$ cm$^2$.
- Question 8 area = $312$ cm$^2$.