Volume = width × height × length.
First let's concentrate on the rectangular prism. This has 4 for its height and 5 for its width so you do 4 × 5 (=20) × 10 (because the length of the rectangular prism is the same as the triangular prism, so we will use the length of the triangular one) = 200m³ for the rectangular one.
To work out the triangular one, it's the same, but whatever answer you get you divide it by 2 because a triangle is just a rectangle cut in half diagonally. Therefore, 3 × 5 (=15) × 10 = 150. Then divided by 2 = 75m³.
Total volume = volume of rectangular prism + triangular prism
Therefore total volume = 200 + 75 = 275m³.
