A regular polygon is rotated 20 degrees about its center, carrying the polygon onto itself. How many sides does the polygon have? 1) 20

2) 8

3) 36

4) 10

36

Step-by-step explanation:

Given that :

Rotation about polygon's center = 20°

To carry the polygon onto itself Angle of rotation is obtained by :

360° / n

Where n is the number of sides in the polygon :

360° / n = 20°

360° = 20 * n

360 = 20n

n = 360 / 20

n = 18

Hence, the polygon has 18 sides or a multiple of 18

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 answer is d=3.09