Answer:
Part 5) 
Part 6) The ratio between the circumference and diameter of a circle, is equal to the number π
Step-by-step explanation:
<u><em>The questions in the attached figure</em></u>
Part 5)
we know that
The circumference of a circle is equal to

where
D is the diameter
we have

substitute


Part 6) What is the ratio between the circumference and diameter of a circle?
we know that
The circumference of a circle is equal to

where
D is the diameter
so
The ratio between the circumference and diameter of a circle, is equal to divide the circumference by the diameter
