Question

Using the formula C = 2πr, find the circumference of a circle with diameter of 28 inches.

Answer 1

Ok so the given is the length of the diameter.
diameter=28 in
so the radius is half the diameter
radius=28/2=14 in
Circumference formula=2 × pi × radius
C=2(pi)(14) - pi can be considered as 3.14 or the value in the calculator
C=28(PI)
C=87.96 in ≈ 88 in
The easiest way is just use the diameter times the pi
Because 2 times the radius is just the diameter
So we can derive that
C= diameter × pi
C=d(pi)
C=28(pi)
C=87.96 in ≈ 88 in

Answer 2

Diameter = 28 inches

radius, r = Diameter/2 = 28/2 = 14 inches.

C = 2πr

C = 2*π*14

C = 28π

C ≈ 28*3.142

C ≈ 87.976

C ≈ 88 inches

Option D.