1. We are given a right-angled triangle with the vertical leg of length $5$ meters and the horizontal leg of length $18$ meters. 2. To find the area of a right-angled triangle, we use the formula: $$\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}$$ 3. Here, we can take the base as $18$ meters and the height as $5$ meters. 4. Substitute these values into the formula: $$\text{Area} = \frac{1}{2} \times 18 \times 5$$ 5. Simplify the multiplication: $$\text{Area} = \frac{1}{2} \times 90 = 45$$ 6. Therefore, the area of the triangle is $45$ square meters. 7. Since the problem asks for the answer to 1 decimal place, the final answer is $45.0$ square meters.