1. **State the problem:** We need to find the volume of a triangular prism with a triangular base of base length 8 m and height 4 m, and the prism length (depth) is 9 m. 2. **Formula for volume of a triangular prism:** $$\text{Volume} = \text{Area of triangular base} \times \text{length of prism}$$ 3. **Calculate the area of the triangular base:** The area of a triangle is given by: $$\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}$$ Substitute the values: $$\text{Area} = \frac{1}{2} \times 8 \times 4 = \frac{1}{2} \times 32 = 16 \text{ m}^2$$ 4. **Calculate the volume:** Multiply the area of the base by the length of the prism: $$\text{Volume} = 16 \times 9 = 144 \text{ m}^3$$ 5. **Final answer:** The volume of the triangular prism is **144 cubic meters**.