Final answer:
The volume of the prism is found by multiplying the cross-sectional area (21 cm²) by the length (3 cm), resulting in a volume of 63 cm³.
Step-by-step explanation:
To calculate the volume of the prism, we use the formula V = Ah, where V stands for volume, A is the cross-sectional area, and h is the length or height of the prism. In this case, the given cross-sectional area A is 21 cm², and the length h is 3 cm. By substituting the given values into the formula, we get:
V = 21 cm² × 3 cm = 63 cm³
Therefore, the volume of the prism is 63 cm³.