Math 7  NYS Math Exam Review Help!
posted by Laruen on .
19. The circumference of the circle below is 25.12 centimeters
***** There is a circle and then there is a line and written radius
C = 2(pi)r
Which is the best estimate for the length of the radius of the circle?
a) 3 cm
b) 4 cm
c) 8 cm
d) 16 cm
please help i tried to solve this problem and I'm struggling (I'm NOT lying)
but i think the answer is b idk ..... I'm not guessing thought
I know haft of 25.12 is 12.56.
Please help
thank you

The formula for the circumference of a circle is:
C = pi * 2r
25.12 = 3.14 * 2r
25.12/3.14 = 2r
8 = 2r
8/2 = r
4 = r 
pi = 3.14
2 pi = 6.28
C = 2 r pi
25.12 = 2 r pi Divide both sides by 2 pi
25.12 / 2 pi = r
r = 25.12 / 2 pi
r = 25.12 / 6.28
r = 4 cm 
Thank You Ms. Sue! :)
Now I understand because I didn't learn this yet in math since we are behind in our curriculum. I'm going to rewrite this so that I way I can use this to study for the exam. I'm going to post more problems (don' worry not too much). I left some geometry questions (about 2) and other problems that I need help with (don't worry it's about 4 more problems or 3 that I'm going to post). Some questions are homework checks to see if I'm correct.
thanks again :) 
thanks Bosnian