Math! Help, please! (Circumferences!)?

The directions are: math the radius or diameter of a circle with the circle's circumference.


1. r=16 in. A. C=8(pie sign) in.


2.d=8 in. B. C=16 (pie sign) in.


3.r=8 in. C. C=32 (pie sign) in.








Please help!





I also have these problems





Find the diameter and the radius of the circle with the given circumference. Use 22/7 or 3.14 for (pie sign).





1. C=25.12 in.


2. C=100.48mm


3. C= 4 2/3 cm.





please show me how to do the problem.

Math! Help, please! (Circumferences!)?
1. C


r=16 in.


C=2(pi)r


C=2(pi)16


C=32(pi)





2. A


d=8in. ~%26gt; r=4in.


C=2(pi)r


C=2(pi)4


C=8pi





3. B


r=8in.


C=2(pi)r


C=2(pi)8


C=16pi





~~~~~





1. C=25.12


C=2(pi)r


25.12=2(3.14)r


25.12=6.28r


25.12/6.28=r


4=r





2. C=100.48mm


C=2(pi)r


100.48=2(3.14)r


100.48=6.28r


100.48/6.28=r


16=r





3. C=4 2/3cm


C=2(pi)r


4 2/3=2(22/7)r


(14/3)(1/2)=(22/7)r


14/6=(22/7)r


7/3=(22/7)r


(7/3)(7/22)=r


49/66=r
Reply:To find the circumference of a circle, just multiply the radius times 2 times pi. Since the radius is half the diameter, you can also multiply pi times diameter. If you do this with the figures that you are given, you will obtain the answers as given. The first part of your question set involves keeping pi in its symbolic or exact form. The second part involves rounding pi to 3.14. Here goes...


1. r = 16 C = 2 x pi x 16 = 32 pi (C)


2. d = 8 C = 8 x pi = 8 pi (A)


3 (try this one yourself!)


For the next few, you have the circumference. Since C = pi x diameter and diameter = 2 x radius, diameter = C divided by pi and radius = diameter divided by 2. So...


C = 25.12 d = 25.12 / 3.14 = 8 r = d/2 = 4


Try #2 yourself


For #3 you'll have to divide by 22/7, that means multiply by 7/22. So...


4 2/3 divided by 22/7 =


4 2/3 times 7/22


Convert the 4 2/3 to an improper fraction 4 2/3 = 14/3


14/3 times 7/22 = 98 / 66 = 49/33, that's the diameter


The radius is half of that, 49/66


Try these yourself, see if you get the same thing.
Reply:The Circumference of a circle is = 2 pi x radius





In your first problems :





r=16in. C= 2 pi x 16


C= 16 pi in. so the answer is '"C"





I think you can do the others, remember that the Diameter of a circle is 2 x the radius.





Next set of problems find the diameter and radius





1. Circumference = 2 pi x r





25.12 in = 2 pi x r





Divide both sides of equation by 2 pi





25.12 in / 2 (3.14) = r





3.99 inches = r





Diameter is 2 x radius 2 x 3.99 = 7.98 inches





You can solve the other problems the same way.