The circumference of a circle is 6.28 inches. What is the circle's diameter

Question

i nees help would u help me out 

Answer 1

First, you should remember that the definition of π is Circumference/Diameter of a circle (π = C/d).  That means that C=Πd.

 

Second, you should recognize that 6.28 inches is a very unusual number (I mean, this is in hundredths of an inch!).  It is what I call a "magic number" -- one that makes the problem very easy to solve so you can concentrate on the procedure.

 

So, C=πd

     d = C/π

     d = 6.28/3.14

     d = 2 inches

Answer 2

Hi Richard.

The circumference, C, of a circle is found by the following equation: C = 2 x pi x r where r equals the radius of the circle (or half its diameter) and pi = 3.14159 (a constant).

Thus, 6.28 = 2 x pi x r 

Solving for r: 6.28/(2 x pi) = r

or: 6.28/(2 x 3.14) = 6.28/6.28 = r

thus r = 1 and since the diameter equals 2 x r, the diameter is 2.