WILL MARK BRAINLIEST Find the circumference of a circular disk whose area 100pi square centimeters.
(to indicate pi, use the word pi and add the measurement spelled out)

Step-by-step explanation:

Let the radius of the disk be r centimeters. Since the area of the disk is 100pi sq cm, we have , and since r is positive, The circumference of a circle is , which, in this case, is .

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional

the first option is the answer.