To find the volume of a right triangular prism after dilation, we first need to calculate the original volume of the prism and then use the scale factor.
Step 1: Calculate the Volume of the Original Prism
The formula for the volume \( V \) of a prism is given by:
\[ V = B \times h \]
where \( B \) is the area of the base and \( h \) is the height of the prism.
Step 1.1: Find the Area of the Triangular Base
The area \( A \) of a right triangle can be calculated using the formula:
\[ A = \frac{1}{2} \times \text{base} \times \text{height} \]
In this case, we can take the sides of the triangle as 3 cm and 4 cm as the base and height (the right-angled sides). Thus,
\[ A = \frac{1}{2} \times 3 \times 4 = \frac{12}{2} = 6 \text{ cm}^2 \]
Step 1.2: Determine the Height of the Prism
The height of the prism is given as 7 cm.
Step 1.3: Calculate the Volume
Plugging the area of the base and the height back into the volume formula:
\[ V = A \times h = 6 \text{ cm}^2 \times 7 \text{ cm} = 42 \text{ cm}^3 \]
Step 2: Dilate the Prism
When a prism is dilated using a scale factor \( k \), the volume of the dilated prism changes according to the cube of the scale factor:
\[ V_{\text{dilated}} = k^3 \times V_{\text{original}} \]
In this case, the scale factor \( k = 3 \):
\[ V_{\text{dilated}} = 3^3 \times 42 \text{ cm}^3 = 27 \times 42 \text{ cm}^3 \]
Calculating that:
\[ 27 \times 42 = 1134 \text{ cm}^3 \]
Conclusion
The volume of the dilated prism is
\[ \boxed{1134 \text{ cm}^3} \]