Using the approximation 3.14 for pi​, what is the radius of a circle with circumference 28.3 ​m?

Question

I do not understand how to answer the question above & would like some help.

Using the approximation 3.14 for piπ​, what is the radius of a circle with circumference 28.3 m?

Answer 1

First, you must realize that each question has a teaching/learning purpose. This question tests whether you know the definition formula for ∏ (that is, pi).

∏ = (circumference of a circle) / (diameter of the circle)

Also, you must know that:

(diameter of a circle) = 2*(radius of the circle)

From the definition of ∏, we get C=∏d [multiply both sides by d)

Then, substituting the formula for diameter into that equation, we get

C = 2∏r

That is where many people would start on ths problem.

Now, divide both sides by 2∏,

r = C / (2∏)

So, C=28.3 m

∏ = 3.14

what is r ?

r = 28.3 / (2*3.14)

r = 4.5 m (rounded)

Answer 2

The formula to find the circumference of a circle is

C=2πr or C=πd

where r is the radius and d is the diameter

Working backwards with the first equation yields the unknown radius,

get the radius on one side of the equation

r=C/2π

then plug in known values

r=(28.3m)/(2*3.14)

plug numbers into calculator and get radius