Find the radius of a circle with circumference of 55.3. Round to the nearest tenth.

Question

I need help solving this problem please!! Anyone know how to solve, and what the answer is?

Answer 1

The equation for the circumference of a circle is:

Circumference = pi × diameter

(or,     C = πd     )

And so for your equation C = 55.3,

So,

C = πd

55.3 = πd

 

So now we can divide both sides of the equation by π to find out what 'd' equals:

 

55.3/π = (πd)/π

55.3/π = d

 

And so since the diameter of a circle is the same as 2 multiplied by the radius, this means that:

d = 2r

So you can substitute this fact into your equation:

55.3/π = d

55.3/π = 2r

2r = 55.3/π

(2r)/2 = (55.3/π)/2

r = 55.3/(2π)

r = 8.80126835...

 

And this number rounded to the nearest tenth is:

r = 8.8