The volume of a right cone is 343π units^3. If its height is 21 units, find the circumference in terms of π.

The formula for the volume of a cone is given by V = (1/3)πr^(2)h, where V is the volume, r is the radius of the base, and h is the height.

Since the volume is given as 343π units^(3) and the height is given as 21 units, we can rearrange the formula to solve for the radius:

343π = (1/3)πr^(2)(21)

Multiplying both sides by 3 and dividing both sides by 21π gives:

r^(2) = (343π * 3)/(21π) = 49

Taking the square root of both sides gives:

r = √(49) = 7

The circumference of the base of a cone is given by C = 2πr.

Therefore, the circumference of the base of this cone is:

C = 2π * 7 = 14π units. Answer: \boxed{14 \pi}.