To calculate the diameter (d) of a circle given its circumference (C), we can use the formula:
\[ d = \frac{C}{\pi} \]
Given that the circumference \( C = 47.1 \) feet and using \( \pi \approx 3.14 \), we can substitute these values into the formula:
\[ d = \frac{47.1 \text{ ft}}{3.14} \]
Now, let's perform the calculation:
\[ d = \frac{47.1}{3.14} \approx 15 \text{ ft} \]
So, the diameter \( d \) of the circle is approximately 15 feet.