#### Answer

$B=13$

#### Work Step by Step

$C=16\pi$
$C=\pi(d)$
$16=d$
$8=r$
In order to determine how many bags we need, we first must reverse-engineer what we already know to find the radius. When plugging 16 pi into the circumference formula, we see that 16 is the diameter. Since radius is half of diameter, half of 16 is 8.
$A=\pi(r^{2})$
$A=8^{2}\pi$
$A=64\pi$
$A=200.96 ft^{2}$
In order to find the area of the garden, just plug the radius into the circle area formula and solve for A.
$200.96/16=b$
$12.56=b$
$13=b$
In order to find out how many bags we need, we need to divide the total area by how many feet each bag covers. Since the number of bags is not a whole number, we need to round up to make sure we have enough dirt. Therefore, we need 13 bags of soil.