Unit 6 Notes #7
Circumference / Diameter Ratio
Name _________________________
Complete the table below by comparing the Circumference and the Diameter of various circular objects.
Object
Circumference (C)
Diameter (d)
Ratio
C/d
page 332
If C is the circumference and d is the diameter of a circle, then there is a number
______such that C
= ____ .
Writing your answer in terms of
If d = 2r where r is the radius, then
C = ___.
.
Sometimes we use a decimal approximation of pi. The decimal approximation is ________
In higher-level mathematics, we leave our answer in terms of pi. Instead of substituting a number and
getting an approximate answer, we use the symbol for pi and treat it like a variable ( similar rules for
adding, subtracting, multiplying or dividing numbers that are written “in terms of pi”
Example: A circle has a radius of 14 m. What is the circumference of the circle?
(write your answer in terms of pi )
Examples:
Examples:
1. If a circle has a diameter of 15 cm, 2. If a circle has a radius of 5.8 cm,
3. Find the circumference of the circle
what is the Circumference? (write
your answer in terms of pi and as a
decimal approximation)
what is the Circumference? (write
your answer in terms of pi and as a
decimal approximation)
(give your answer in terms of pi).
4. Find the diameter of the circle.
5. Find the diameter of the circle.
6. Find the distance around the
outside of this figure. (write your
answer in terms of pi and as a decimal
approximation)