Answer:

Step-by-step explanation:
The given sequence is
-12,-16,-20...
The first term of this sequence is
.
The common difference is


The nth term of this arithmetic sequence is;

We substitute the values for the first term and the common difference to obtain;

Answer:
395.85
Step-by-step explanation:
If the diameter is 12, then the radius must be 6. Following the formula of pi: 2 * pi * radius, our result is 37.7. 37.7 * 10.50 is 395.85
I really hope this helps. My memory of circles and pi isn't the best.