How do you find the circumference of a rhombus?

Well, "circumference" is a word that's reserved for circles.  If you want
the distance all the way around a rhombus, that's called the "perimeter"
of the rhombus.

To find it, you need to know the length of one side. Then, since a rhombus
has  4  sides and they're all the same length, you just multiply the length you
have by  4 .

Part A: Using the formula for circumference, solve for the value of pi for each circle.

Formula of circumference: C = πd

Circle A:

π = C/d = 21.98 / 7 = 3.14

Circle B:

π = C/d = 18.84 /6 = 3.14

Part B: Use the formula for area and solve for the value of pi for each circle.

Formula of area: A = πr^2

Circle A:

A = πr^2 where r = d/2 = 7/2 = 3.5

π = A/r^2 = 38.465 / (3.5)^2 = 38.465 / 12.25 = 3.14

Circle B:

A = πr^2 where r = d/2 = 6/2 = 3

π = A/r^2 = 28.26 / (3)^2 = 28.26 / 9 = 3.14

Part C: What observation can you make about the value of pi for circles A and B?

The value of pi for both circles A and B are the same as 3.14.

So it doesn't matter how big or small the circle is, the value of pi always remains the same.