Friday, January 29, 2010

Circular Circles

Circles are everywhere!

In our class, we are studying geometry, and
we are learning about circles.

We have learned that circles have a center point. In addition, we have learned that a line segment drawn from the center point to the outside edge of the circle is a radius.

The diameter is a line segment that extends from one side of a circle to the other,
right through the center point.

Lastly, we learned that the perimeter, or outside edge of a circle, is called the circumference.

We used chalk tied to a piece of yarn to draw a giant circle outside our classroom. Later we measured its radius which was 9 feet in length. Since the diameter of a circle is two times the radius, we determined that our circle's diameter was 18 feet.

After we drew and measured our class circle, each team drew their own.

Way to go, Team 4!

Then each team measured the radius of the circle in inches.

Each team's circle had a different radius, and of course, a different diameter!

Good for you, Team 2!

Great job, Team 1!

Super work, Team 3!

Excellent job, Team 5!

Great work, Team 6!

We used multiplication or addition to double the radius
and find the length of the diameter.

* * * * *

Back in the classroom after we were finished, Mrs. Ranney showed us how to convert the inches to feet.
She showed us how to divide by 12, the number of inches in a foot.

For example, one team's diameter was 88 inches, so we worked this problem:

88 divided by 12 = 7 feet 4 inches

* * * * *

How do you like our circles? What circles can you find around your house?
Try measuring the radius of a circle you find at home and let us know what the measurement was.
Remember, to find the diameter, double the radius!


  1. Dear Mrs.Ranney,

    I found a circle, and my mom and I measured it. It was in my mom's room where her pictures go. The radius is 13 inches long,or 1 foot 1 inch. Its diameter is 26 inches long, or 2 feet 2 inches.


  2. Dear Carson,
    You are a super blogger!! I'm glad you found the post and that you found a circle. You did a great job of measuring the radius and computing the diameter.
    Keep up the great work.
    Mrs. Ranney

  3. Dear Mrs. Ranney,

    I thoroughly enjoyed reading your post about circles. Who knew there was so much to learn about a circle? Radius, diameter, center, circumference. Circles are really special!

    I am looking at a circle right now. It is a circle on the front of my iPod, and it has a diameter of 1.5 inches.

    Tomorrow I am going to wear a necklace that has many circles linked together! Look for it!

    Thanks for a great post!

    Mrs. Yollis

  4. Geometry was my favorite part of math when I was
    in school. I enjoyed it because it was very visual
    and art was my passion. Seeing numbers related to
    shapes was great for me. Keep having fun with math!!
    Mrs. Coblenz

  5. Dear Mrs.Ranney,

    I found a clock that is shaped like a circle. It is in my mother's office, and it helps her get to work on time. The radius is 6" and has a silver rim that is 2" wide, the diameter is 12" long.


  6. Dear Mrs. Ranney,

    I found a CD music disk in my family's office. I measured with my dad, and it was 4 inches in diameter, and the radius is 2 inches long.


  7. Dear Mrs. Ranney,

    I found a circle in the kitchen. It was the old teapot. I found It at the bottom of it. The diameter was 14cm. The radius was 7cm. I think circles are an awesome shape.

    Your Student,


  8. Dear Mrs. Ranney,

    I found a circle in my kitchen.It belonged to the kitchen table where we sit for breakfast and dinner each day. The diameter of the circle is 42 inches, or 3 feet and 6 inches. Its radius is half the diameter so it is 21 inches which is 1 foot and 9 inches.

    I love finding diffrent circles at my house. See you tomorrow!



  9. Dear Mrs. Ranney,

    I loved learning about the diameter and radius in a circle. When I looked arouned the house for circles I found one on a plate. The radius is 5 inches long and the diameter is 10 inches long.

  10. Dear Mrs. Ranney's class,

    I enjoyed reading your post! We have been going over all the geometry skills lately in class. I almost forgot all the terms! Keep up the good work!

    Brendan K.
    (5th grade)

  11. Dear Mrs. Ranney's Class,

    I love the fact that you are learning about measuring circles. In fact, for RTI our class switches to Mrs. Constantino's class for measuring circles. Did you guys learn about chords yet? Anyway, I love the fact that you're measuring circles.

    Cameron(Mrs.Coro's Class)

  12. Dear Mrs. Ranney,

    I found a circle on my kitchen table. It is the bottom of a vase. The diameter is 4 inches long, and the radius is 2 inches long.

    Your Student,

  13. Dear Mrs. Ranney,

    I found a circle in my house. It is the front of a circle clock. The diameter is 3 inches long or 7 1/2 centimeters long, and the radius is 1 1/2 inches, which is 3 3/4 cm.


  14. Dear Mrs. Ranney,
    I had a great time learning about geometric shapes!!! I had several circles in my living room, but my favorite, and most interesting, is a plate with red and gold printing on it. The diameter measures 10 1/2 inches. The radius measures 5 1/4 inches.

    Andrew S.

  15. Dear Mrs. Ranney,

    Hi this is Jae won. I am in 5th grade, and now English is getting easier. I saw the circles, and they were really cool!

    Jae won

  16. Dear Mrs. Ranney's Class,

    Wow! I didn't know there were so many circles everywhere. At home, some circles I have never noticed before are my camera lens, my power button on my computer, my nostrils, my pupils on my eyes, and my window.

    Noah (Mrs. Coro's class)

  17. Hello class,

    I really like circles since every time I find a different way to have fun with them I find like 1,000,000,000,000,000,000 other ways to have use for them !! I really like them because you can hypnotize people with them!!!



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