Answer:
Circumference of the circle: 

Ratio of the circumference to the diameter: 

Explanation:
First, we are finding the circumference of the circle using the circumference formula:

were
 is the circumference of the circle 
 is the diameter of the circle 
We know from the problem that the diameter of our circle is 12cm, so 
. 
Replacing values: 



Now, to find the ratio of the circumference to the diameter, we just need to divide the circumference of our circle by the diameter:
ratio = 
