The volume \( V \) of a rectangular pyramid can be calculated using the formula:
\[ V = \frac{1}{3} \times \text{Base Area} \times \text{Height} \]
For a rectangular base, the area can be calculated as:
\[ \text{Base Area} = \text{Length} \times \text{Width} \]
Given:
- Length = 30 cm
- Width = 20 cm
- Height (Altitude) = 40 cm
First, calculate the base area:
\[ \text{Base Area} = 30 , \text{cm} \times 20 , \text{cm} = 600 , \text{cm}^2 \]
Now, substitute the base area and height into the volume formula:
\[ V = \frac{1}{3} \times 600 , \text{cm}^2 \times 40 , \text{cm} = \frac{1}{3} \times 24000 , \text{cm}^3 = 8000 , \text{cm}^3 \]
Therefore, the volume of the rectangular pyramid is:
\[ \boxed{8000 , \text{cm}^3} \]