Question

The circumference of a circle varies directly with the radius. A circular pizza with a radius of 3in has a circumference of about 18.84in. Write the equation using direct variation that relates the circumference, C, to the radius, r. What is the circumference, in square inches, of a personal pizza with a radius of 2in?

Answer 1

C=6.28r, the circumference is 12.56 inches

Explanation:

We are given that the pizza's circumference, C, varies directly with the radius, r. This means

C=k⋅r

for some constant, k.

Since a circular pizza with a radius of 3in has a circumference of 18.84in, we substitute these values into the formula for direct variation to find

18.84=k⋅3

Dividing by 3 gives k=6.28, so an equation that relates C and r is

C=6.28⋅r

Substituting r=2 yields

6.28⋅2=12.56

So a personal pizza with a radius of 2in has a circumference of 12.56in.

Answer 2

c=kr

c=12.56in when r=2in

Explanation:

Circumference (c) of a circle varies directly with radius(r)

Equation that relates the circumference and radius is

c=kr

Radius=3in

Circumference=18.84in

18.84=k*3

k=18.84/3

k=6.28

Find circumference when radius=2in

c=kr

c=6.28*2

=12.56in

c=12.56in