The circumference of a circle with a radius equal to r is given by the expression 2*pi*r.

Here, we are given the circumference and have to find the radius. Let the radius be r

2*pi*r = 72*pi

=> r = 72*pi / 2*pi

=> r = 36

**The required radius is 36**

We will use the the circumference formula to calculate the radius.

We know that:

C = 2*r * pi where c is the circumference and r is the radius.

Now we will substitute with c = 72 pi.

==> 72*pi = 2*r*pi

we will divide by pi.

==> 72 = 2r

Now we will divide by 2.

==> r = 72/2 = 36.

**Then, the radius of the circle is 36 units.**