To find the height of the rectangular pyramid, we will use the formula for the volume of a pyramid, which is given by:
\[ V = \frac{1}{3} \times B \times h \]
where:
- \( V \) is the volume of the pyramid,
- \( B \) is the area of the base, and
- \( h \) is the height of the pyramid.
For a rectangular base, the area \( B \) can be calculated as:
\[ B = \text{length} \times \text{width} \]
Given:
- Length \( = 7 \) cm
- Width \( = 9 \) cm
Calculating the area \( B \):
\[ B = 7 , \text{cm} \times 9 , \text{cm} = 63 , \text{cm}^2 \]
Now, substituting \( B \) and \( V = 231 , \text{cm}^3 \) into the volume formula:
\[ 231 = \frac{1}{3} \times 63 \times h \]
To isolate \( h \), first, multiply both sides by 3:
\[ 3 \times 231 = 63 \times h \]
\[ 693 = 63h \]
Next, divide both sides by 63 to solve for \( h \):
\[ h = \frac{693}{63} \]
Now performing the division:
\[ h = 11 \]
Thus, the height \( h \) of the pyramid is:
\[ \boxed{11 , \text{cm}} \]
In conclusion, the height of the pyramid simplifies directly to 11 cm based on our calculations.